If we’re going to look at it like that, I’d say this is a case the order of factors does alter the result. Caring about fairness and harm only if they do not affect imagined purity, only within your own group, and only when authority says you should… isn’t so much caring about fairness and harm as caring about not getting kicked out of the group for pissing the rest off.
What I am saying is that your attempt to create an artificial question fails, because if you actually, asked /in real life/ that question, I would still be your friend. Your attempt at a fake insult fails because you choose to invent something that I deal with /in real life/.
If you want to invent a insult, and ask “would you object to this less on FB than in real life”, you have to make up something insulting that I would actually object to in real life.
Of course, this is all just a straw man, because the actual question was "In 2018 are political differences a dealbreaker WRT to new romantic relationships? ", not “are insults a dealbreaker”
How many of your friends who say they hate Americans are actively working to make life worse for Americans? Like, are any of them campaigning to get Americans kicked out of Australia? Or limit the amounts of rights or government services American-born Australians can access? Because, yeah, if its just guys talking shit over beer, that’s pretty easy to ignore. That’s also not really equivalent to supporting policies and candidates that are going to directly target your rights, and which have a very real chance of becoming law.