May you have peace!
You absolutely can use the Bible to refute Jehovah's Witnesses' claim that they are who they are... in a plethora of ways... some of which I will share below. Before doing that, however, I must say to you that the "veil" that allows them to be "blind" is not easily removed and so you must realize that although the Bible says what it does, that they will "see" it is not guaranteed. For your peace of mind, however, I will proceed; please note that I will use the NWT Reference Bible (with footnotes) so that your father, if he is inclined to look up the scriptures and verses, will not be able to claim that it is the Bible version that is at fault.
First, please let your father know that contrary to what they claim... the WTBTS... and "the Society"... is NOT the truth. In calling themselves such they are liars, for only one has the truth... and IS the Truth. You cannot get to God by joining with them, for there is only ONE Way to come to God. John 14:6
Second, that "veil" that blinds them... is the Law Covenant... and those who attempt to live by it (and hypocritically demand that others live by it although they themselves transgress it, for if you transgress one... you transgress them all)... are "veiled"... blinded... so that the glorious good news... about the Christ... the One who is Life... and GRANTS life... cannot shine through. The Law Covenant... condemns to death. The Law... of the Christ... which is LOVE... leads to life. The Law Covenant condemns the flesh; the Law of the Christ... grants life... to the spirit.
2 Corinthians 3:12-18
Now, with regard to disfellowshipping:
This was something that the Jews distorted and bastardized, based on the requirements of the Law Covenant to remain "clean," and Paul perpetuated due to his education as a Pharisee (Jewish religious leader). At 1 Corinthians 5:9-13, Paul is recorded as admonishing the Corinthians to "quit mixing in the company"... those "brothers" who engaged in wrongful conduct, telling them to "remove the wicked man" from among them. That, however, was NOT in line with the teaching of the Christ, and Paul, after being corrected by the Apostles, recanted. At 2 Corinthians 2:1-11, Paul recognized that he had overreacted and harshly so, so that rather than being able to forgive the man in question, the entire congregation was saddened by the turn of events: according to Paul, they now had to "hate" their brother. That saddened them because that is NOT what they had been taught by the Christ. Paul, however, did not walk with the Christ while that One was on earth, and so had to LEARN love over time. He did not know it at the start.
His directive, then, was a problem for the Corinthians. They ignored it the first time he wrote, so that he wrote again (1 Corinthians was his second letter to them!) Why was this such an issue with the Corinthians? Because contrary to what the Pharisees taught their followers... to hate and look down on those not like them as well as those considered "unclean" ... my Lord taught his disciples to LOVE all... even the "unclean"... even their enemies.
Matthew 5:43-48
When the "unclean"... in flesh and in spirit... were brought to him... he did not turn them away... but either HEALED them... or FORGAVE them... which CLEANSED them. Always. Without exception, excluding the scribes and Pharisees. And he gave his disciples the authority... and commandment... to do the same. For if they wanted to be shown mercy for THEIR sins and errors, they were bound and obligated to SHOW mercy to all others.
John 20:22, 23; Luke 6:37; Matthew 6:14; Mark 11:25; Matthew 6:14
The WTBTS, however, teaches its followers not to be mixing with ANYONE not like them... whether those of "the world"... or those who they call "brothers," as well as those who have either committed some error of flesh or spirit, or who don't agree with them. If one were to TRULY follow the Christ, however, as they claim to, one would know that the Christ himself was always to be found AMONG the sinners... for, as he said, he came to SAVE sinners and not righteous people. Why? Because righteous people have no NEED of a savior - if they are so righteous, so clean... they can save themselves. Right?
Paul said: "Quit mixing in company with anyone called a brother that is a fornicator or a greedy person or an idolator or a reviler or a drunkard or an extortioner, not even eating with such a man."
My Lord, on the other hand... was always to be found with the sinners... eating AND drinking with them. Matthew 11:19; Luke 15:2
He freely forgave the sins of adulterers/fornicators. John 8:1-11
He chose both a greedy person (Judas, who coveted money) and a reviler (Peter, who returned an evil for an evil) to be his apostles. John 18:10
He invited himself to dine with an extortioner (Zacchaeus) at that one's house. Luke 19:1-10
And he forgave a thief in the last hour. Matthew 27:38
Who are we to follow, then? Paul... who only after severe trial for the sake of the Christ, came to know LATER what love was? Or the Son of God, the image of the invisible God, the exact representation of His very being, who demonstrated the goodness, mercy and loving kindness of God so that he could say, "If you've seen ME... you've seen God" and "The Son cannot do a single thing of his own initiative, but only what he beholds the Father doing. For whatever things THAT One does, these things the Son also does in like manner."? Matthew 23:10; Hebrews 1:3; John 14:9; John 5:19;
If you will, please ask your father (and ask him to ask those he follows): is Paul the image of the living God... or is Christ? Did Paul leave us his footsteps to follow in closely... or did Christ? Is the pattern set by Paul the one we are to imitate... or is it the one set by Christ?
Like so many others, the WTBTS has chosen Paul as their "leader" - they refer to his teachings and writings more than that of any other. Why? To use them... to mislead, if possible, even the chosen ones. They teach that Paul was chosen because he was a zealous man; however, that is entirely false: Paul was chosen... to pay his debt to God - he had "persecuted" the Christ by persecuting those who belonged to the Christ, delivering them up to be murdered. Paul was accountable for their blood. To pay off this debt, then, he was called to SLAVE for Christ: his life... in exchange for those he had betrayed. Acts 9:1-6, 15, 16.
As regard disfellowshipping, how does my Lord view it? Well, once, when a man was disfellowshipped ("expelled") by the Pharisees, rather than shun such one, my Lord went himself to look for the man. I invite you to read Chapter 9 of the Book of John, particularely verses 34 and 35.
Now, some JWs will argue that this does not count, because the man was innocently expelled by evil Pharisees and that this would not occur among them. That, too, is a lie, for they regularly "expel" folks from their "synagogues" (public meeting places) for claiming to have been given sight by the Christ. I know... I was one of them. My Lord opened my blind eyes... so that now I see. True, the man's case was physical sight and mine is spiritual... but sight... is sight. Yet, when I confessed it to the pharisaical leaders of the WTBTS... I was expelled; disfellowshipped. And directly after, my Lord came... and found me... and revealed himself to me... just as he did to that man.
The men your father follows... are false "christs"... meaning they are false anointed: they have NOT received holy spirit from God through Christ. And there is one way in particular for you to know this: they shut up the kingdom of the heavens before men. They're not going in, nor do they allow those on their way in to go in. How is that?
There is only ONE Way into the kingdom: through Christ. Yet, rather than direct you to him, they direct folks to themselves and their "golden calf," a visible form of worship manifested in "The Watchtower Bible and Tract Society of Jehovah's Christians Witnessess"... yada, yada. In particular, they block that Way by PROHIBITING one of the foremost means and commandments that Christ gave to his disciples:
"UNLESS you eat the flesh of the Son of Man and drink his blood, you have NO LIFE in yourselves." John 6:53
My Lord stated that IF one ate and drank, one would live forever. That IF one ate and drank, one would be resurrected. That IF one ate and drank... one would be in union with him.
John 6:48-56
And yet, they teach 99.99% of their followers that they are NOT to eat and drink, that such is reserved for a few, a small group, and that others will live forever, be resurrected and be in union... WITHOUT eating and drinking. In direct OPPOSTION to what my Lord himself stated... which is recorded in the Bible! They entirely disregard that ALL who left Egypt... Israel and the "vast mixed crowd" alike... ate the manna... and drank from the rock mass that was the Christ. Numbers 11:4-6; 1 Corinthians 10:1-4
So, the question for your father... indeed for all those like him, sheep without a TRUE shepherd... who are we TRULY to follow? Earthling man (the WTBTS)... who follows earthling man (Paul)... who followed the Christ? Or simply... the Christ? If he is our mediator, why on EARTH do we need another? True, many are sent to tell about the Christ, but like John the Baptist, that is ALL they are to do: tell about him so that others are led to HIM... and not to themselves or those who herald him.
This is just a fraction of what the Bible contains that is in opposition to what the WTBTS teaches. And yet, even this is very important. I truly hope this information is of assistance to you, if not to your father, and I wish you the greatest of peace.
Your servant and a slave of Christ, truly, by means of holy spirit,
SJ
