"Wow, so what you're saying is you won't love me if I come in and release millions of angry wasps in your home? Have fun in your echo chamber, I guess."
They appeal to tolerance because we value it, not because they do. Once they have power they won’t practice the tolerance towards differences in opinion they demand.
Unlimited tolerance must lead to the disappearance of tolerance. If we extend unlimited tolerance even to those who are intolerant, if we are not prepared to defend a tolerant society against the onslaught of the intolerant, then the tolerant will be destroyed, and tolerance with them.—In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise. But we should claim the right to suppress them if necessary even by force; for it may easily turn out that they are not prepared to meet us on the level of rational argument, but begin by denouncing all argument; they may forbid their followers to listen to rational argument, because it is deceptive, and teach them to answer arguments by the use of their fists or pistols. We should therefore claim, in the name of tolerance, the right not to tolerate the intolerant.
It's worth noting that what Karl Popper most likely meant by intolerance is something like "forbid their followers to listen to rational argument ... teach them to answer arguments by the use of their fists or pistols" rather than any broader meaning of the term, and is here explicitly giving credit to the value of rational debate.