The parent to me comment was complaining about the attitude of left-wing people towards bigots. I'm leveraging my knowledge of extremism to explain why left wingers feel such antipathy towards bigotry: because of the genocidal outcomes which are associated with it and nowadays actively promoted by some folk.

Of course, extremism is by no means limited to one particular ideology. I'm not a fan of Maoists, for example.

I believe one can certainly change their views, although it's hard work.