Differences of opinion

When is a difference of opinion merely a difference of opinion, and when is it a matter for exclusion of the person who holds that opinion from polite society?

I came across a couple of things the other day that explained really well why no-platforming of actual Nazis is a good idea.

One is that it actually works: starving them of the oxygen of publicity makes it impossible for them to attract adherents. The example given was that of Oswald Mosley’s Blackshirts in the 1930s in the UK. When n...