That doesn't work. There are lots of people who are extremely intolerant to people who hold views that weren't very controversial a decade or two ago and are still widely held today; case in point, Brendan Eich (and the intolerant campaign that got him fired). "Unacceptable intolerance" is something that can have very different definitions from one person to the next, so it's not a useful test.
> It is not really that hard.
Drawing the line about what the limits of free expression are in an open society is a very hard problem. Saying it isn't is flippant and frankly wrong.
> The irony in this whole thing is, the more tolerant you are to an inherently intolerant ideology like white-supremacy, the less tolerant we become as a society.
That isn't true either, it can also show societal confidence that ideas like white-supremacy are wrong and that the light of scrutiny will make them look foolish.