Even though the witnesses say that you should prove the truth to yourself, or whatever, many people don't because they don't feel the need to prove it to themselves. The indoctrination is so cemented into their minds already that it is the "truth", that many people do not even begin to question anything until they see bad conduct that directly contradicts with what should be in "Jehovah's organization". I think this is especially true if you grew up a JW.
Also, it sounds like your son has very black and white thinking right now, which is carry-over from the JWs. That's the only way they think. Hopefully, with some time and distance from the borg, he will see that not ALL of the JWs are bad, and not everything is either good or evil. I would tell him that if he really wants to distance himself from what the JWs have taught him, he will have to let go of the black and white thinking.