One angry justification for disrupting the play goes like this: liberals do this to conservatives, so this is fair play. We’re just imposing liberals’ rules on liberals. Liberals disrupt conservative speakers on campuses all the time, and if that’s okay, why isn’t this okay?
This way lies madness and destruction, the excuse to abandon everything we believe. We follow our principles because they’re right, not because everyone agrees with them. We follow them in adversity and in the face of opposition and even injustice. We give due process — a jury trial — to a cop who shot a motorist even if a very good argument can be made that the cop executed the motorist without due process. We defend the free speech of Nazis and communists who would deny it to us if they had power. At one point, I would have been able to say that we don’t torture people even if they torture.
The “eye for an eye” theory of respecting free speech is particularly pernicious because it represents the worst sort of collectivism, something the principled Right ought reject. Note that people who say “apply the Liberals’ own rules to the Liberals” aren’t disrupting, say, an Antifa rally or the meeting of some Berkeley student group that advocated shutting down a conservative speaker. They’re disrupting other people entirely, on the theory that everyone they deem part of the nebulous collective “Liberal” deserves to be silenced because someone else in that nebulous collective engaged in silencing behavior.