Those who blindly followed Pharisees were illiterate and/or ignorant of the Law. It wasn't common for the average Joseph to have access to the scrolls of Scripture. Pretty much until proliferation of Bibles was achieved in the relatively-recent past, people had an excuse to blindly follow their religious leaders. After the invention of the printing press and the Reformation, leaving your faith to your church became unfathomably lazy. Claiming to follow a book you've never read became unforgivable.
Unless you're wearing a styro-foam helmet and licking the windows, there is no acceptable reason to be in a nutty cult. Granted, many JWs are just shy of that situation and functionally illiterate. Many people in most churches haven't a clue what they just read when they read from the Bible. This situation is ripe for charlatans claiming the priesthood to come along and "explain" the scripture. They use some synonyms for a few of the words in the passage to make it sound like they're just explaining, while butchering the meaning and - voila! - the outcome is completely contrary to the original text.
I encountered this at my door with some JWs who insist Judas wasn't present for the Last Supper. John implies and Luke outright states that Judas was present when the bread and wine were blessed and passed. However, the JW version is that Judas left beforehand. They give their timeline and jump around in the Gospels to get the scriptures they want in the order they want them in. They similarly jump around in Mat 24 to get the order of events they want. JWs don't even bat an eyelash the blatant lies, because they're relying on the Watchtower to dumb it down for their defective, idiotic brains to slowly digest.
Anyone intelligent enough and/or paying any attention will quickly notice things aren't kosher between the Bible and the Watchtower version. These people are labeled "apostates" and quickly and quietly removed, so they won't alert the dumb-asses in the congregations. The Bible isn't written in Swahili (well, I'm sure some are; but I'm talking about in my congregation), so even the biggest dolt can eventually be shown that it proves the Watchtower to be a liar. It's really hard to have sympathy for grown-ass adults who choose the lies over the truth.
Jesus wasn't angry with the Pharisees for being mistaken. He was pissed at them for being liars. JWs are liars and they know it. For example, in the "Bearing Thorough Witness" book, they openly admit the second sacrifice of the day - which the Bible says is to be "between the evenings" - is about 3 pm. When they talk about Nisan 14 being Passover, they insist "between the evenings" is after sundown. They've been around for 130 years and Passover has been celebrated by Jews on Nisan 15 for thousands of years. You think nobody has brought this to their attention? They know they're lying and keep right on doing it. Feel sorry for them? God himself will not feel sorry for them and He is love.