It was a U.S. Supreme Court judge who came up with a phrase about free speech does not give you the right to shout ‘fire’ in a theatre when there is no fire. A great many people who hear that decision today think it sensible but when you then explain that this was just part of a summing-up that silenced a man from speaking against being drafted for a war he disagreed with, suddenly many people’s perspectives change.
So we can’t censor speech just because there are words we find ‘offensive’. If a word by itself is offensive that is our individual problem, not the speaker’s. We can’t say “but most people would be offended by someone effing and blinding” because that is just saying that it is OK to censor someone from saying something the majority don’t like to hear, which is not free speech at all.
Maybe the bus company, as a private business, can have rules about language used on their busses. But think about that: we don’t allow that business to have rules about which race can sit at the front of the bus and are we really saying that (mis)using words is a more important wrong than telling someone to get to the back of the bus?
Absolute free speech does have its problems. Anything but absolute free speech tends to have much bigger problems in the long term.