OK, the Paradox of Tolerance is a Karl Popper social theory about how society should feel about its subgroups, and made recently famous again in a comic, although I don't think the comic context is relevant to this meme.

The basic idea is that if we tolerate absolutely every subgroup, then we are logically also tolerating the existence of fascists and other types of subgroups that want or promote intolerance. If one of these groups (let's say, Nazis) is tolerated by society, it may gain control--indeed, to Popper, this is inevitable--and society becomes intolerant again. So paradoxically, tolerating everything led to the collapse of tolerance itself.

His remedy is that we must not tolerate the intolerant, we must extinguish groups like that through various means. To be clear, Popper is NOT saying we must kill or commit violence against the members of those groups, just that we must make sure the group structure itself is dismantled as it's being built in every case. And here we get to the rather terrible point being made by the meme. "Minorities", as the meme puts it, would be the Nazi group from the earlier example, because their viewpoint is a minority. And Popper isn't promoting violence against them, unless you consider the enforcement of laws to be inherently violent. (A valid point of view, but very far from what the meme is suggesting.)