But that's not even what his argument is, it's much more bizarre. If I understood correctly, he claimed that

1) Intolerance of intolerance is tolerance.

2) Every modern philosopher agrees with #1.

Both a false statements, as far as I can see.

As for "Intolerant behavior", it's a completely subjective concept that is orthogonal to morality. In most places in Saui Arabia it's not tolerated for a woman to not appear wrapped in a bag, and considered immoral too, but I consider that kind of treatment of women completely intolerant and immoral in itself.

The thing : #1 was wrote by Popper, a rather known utilitarist (well, negative utilitarist: every action, instead of optimizing overall happiness, should aim to decrease overall pain). There is a lot of modern philosopher that agree with this as well. This is a catchphrase, it doesn't refer to what you read but to the reflexion behind (like "i think therefore i am" refer to cartesian doubt and that you can doubt of anything except the fact tht you exist).

HS: The main issue with that, a sentence that resume an "essai" (don't have a clue about the english translation), is that people that do not know what philosophy really is. Let's be honest, if it is taught as well in the world than in France, almost nobody knows. So most people misunderstand what it really means, while some of the other use this knowledge to put people down. Even writing this, i'm pedantic, and i really don't want to be, so imagine someone who like feeling full of himself? And that way, more and ore people hate philosophy and philosopher, and get disinterested. (i wrote like a hundred lines about philosophers in French media, but i'm sure no one care so i will refrain...)