Thinking about this paradox a bit more, the exact limit between 'this tolerant society will tolerate all these intolerants' and 'this society will no longer be tolerating them', is when the intolerants start silencing their opposition. What I mean by 'silencing' is something like murder, or threats of murder, or basically just ways in which you can get other people to not get a say anymore.

For indeed, if the intolerant don't silence their opposition in any way, then they have no way of 'destroying the tolerant'. To 'destroy the tolerant', they necessarily have to do something that 'silences' another person. So the paradox doesn't take effect. The tolerant society can continue just fine and will continue to be tolerant.

Conversely, if society is intolerant of all ways of silencing people (whether by killing them, or any of the other things), then whenever a bunch of intolerants tries to destroy the tolerant, society will fight back (which will take the form of arresting them, locking them up, etc.) so the problem should be solved.

So basically, the exact point at which /r/The_Donald (or anything else for that matter) should be removed is when they start trying to 'silence' people.