Earlier quoted context omitted.
You can start by saying what ideas of his you think are wrong, and why they are wrong. Then you can listen to why he (or those he agrees with) believe those ideas are right.
If I think your ideas are morally wrong and getting people killed, I am compelled to either try and stop you, or resign myself to cowardly inaction. I of course choose cowardly inaction—I’m selfish and enjoy the comfort of my life and don’t want to disturb it. But I don’t try to make that out to be a virtue!
Further, by not engaging, you miss the opportunity to present why you think his ideas are wrong. If people hear both sides, they can make an informed choice. If they hear neither side, they can only make an uninformed choice. If you think this arrangement benefits you, I would question how confident you are in your beliefs.