TBH, you sound an awful lot like C already. Perhaps that's why I like you. Beneath the far-Left veneer, you're actually a pretty cool guy with a sense of humor, and respect for freedom of speech.
Person B did not call A a "dumb cunt." That's not the hypothetical. He ordered A to "shut the fuck up." A and B are probably going to get in a fight. C will probably have to break it up and lecture them both on the need for tolerance and respect.
You got person C all wrong. Person C pays his bills, shows up to work on time, gets the job done, and takes care of his family. He just came to the bar to unwind. He's not trying to start trouble. He probably thinks A is a kook, so he stopped listening after a few seconds. But when C hears B tell A to STFU, he has no choice but to step in. C is the adult in the room. Now he is forced to tell B "back off dude, this ain't the Soviet Union. A gets to speak. Leave him alone."
C is likely very popular with most people. The ladies love him, although he stays faithful to his wife. He's an exemplary dude.