Because there are alot of people that agree with him.

Pushing back against him is good for multiple reasons. One, it makes clear to his followers what'll happen to them if they start spouting off their opinions in public - or, worse, making those opinions a reality by escalating to violence. If we cut people like them off here, now, we ameliorate alot of potential trouble in the future.

Two, he's a smug, sanctimonious, evil, retarded asshole who hasn't thought his own opinions through to the ultimate conclusion. ('Oh, you're saying that it's okay to murder people to achieve political aims? So... what stops people from doing the same to you?') Having him end up ruined and penniless is the nice option as to what his overall philosophy will end up at.