> 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.

Note that Popper is not claiming that "fists or pistols" are a necessary condition for not tolerating intolerance: they're a final stage of said intolerance. Popper explicitly says that we might reserve the right to preempt intolerance before it reaches the point of its followers resorting to violence.