The main message of the TRUTH may be the same but if the main message is all that matters to God then any religion that believes he exists and that he sent his son to die for our sins, would be a religion that is pleasing to him. If that is so then why don't JW's go from door to door with that simple message?
Instead the WTBTS has gone to great lengths to demonstrate that for JW's this belief isn't enough. The truth is in the fine details rather than the big chunks as your friend believes. This is why they have had to become a publishing company that spews out reems upon reems of paper explaining their TRUTH and why everyone else is false religion and hated by God only to find out that much of what they called the TRUTH wasn't true afterall. As one of Jehovah's Witnesses it isn't enough for your friend to simply believe that God exists and his Son died for us. He/She is expected to believe all the details they provide without question and to spread it to others, right or wrong until told to do otherwise.
This person is in denial at this point and it might just be an exercise in futility to even try and discuss this with them.