Non-infectious ignorance can be left alone. A state senator with a PR platform, using it to spread ignorance of a sort that ruins millions of lives, cannot be left alone in good conscience.
But unfortunately points of view aren't innocent things that everyone is entitled to. They can cause SERIOUS damage to the lives of other people.
If I have a point of view that binder clips should be made illegal because they're hideous, and manage to make that a law, then A: My point of view is making regular stationers criminals, and B: I might have put people who make binder clips out of work.
Everyone has a point of view, but not all of them are reasonable, and simply having them can screw other people up.
I agree with you in the sense of allowing people the space to disagree, but in this particular case, someone's bad opinion, if left unchallenged, could result in other people going to jail. It's the principle of reciprocity.
Think of it this way: he's not attacking the politician for her opinion. He's attacking her for attempting to make her stupid opinion into a matter of public policy.
Everyone is welcome to have their opinions. When one attempts to act on those opinions in a way that's harmful to other people, one cannot but expect others to oppose.
Let's say I believe that three-year-olds can fly if only they're forced into a situation where they must do so in order to save their lives. It's a stupid opinion, but it's harmless if it's just a thought sitting in my head.
Now let's say I decide that I need to teach a bunch of three-year-olds to tap their innate flying ability by throwing them off a bridge. Is stopping me from doing so disrespectful of my opinion? Would that actually give you pause in stopping me?
Respecting someone's opinion is fine and dandy, but your inalienable right to your opinion stops when it starts motivating action involving others; at that point, the general rules regarding your rights when interacting with other people apply.
My conscience is better off letting someone have a right to their own opinion (albeit a poor one), rather than attacking them for it.
In other words, I'd rather choose to understand where their point of view is coming from and accept it, than to try and change it.