But how does that matter? You're saying that "we consider painting your face black offensive if you're white, and you should stop doing it".
And now you know this Swedish thing that you're doing is offensive, because i just told you. Do you stop doing it?
Or would you say that "this isn't actually offensive in the US, and i'm in the US. But i'll be sure to never do that if i ever visit Sweden. Thank you for the information."
I'm not saying you
have to stop doing it.
You can be as offensive as you like. In fact, I merely remarked that the party attire was moronic and the blackface was in poor taste; the words, 'and you should stop doing it', never entered my posts.
Personally speaking though: If the pain the Swedish activity brought to others was serious enough,
and the only reason people I knew were doing it was to revel in infantile cultural stereotypes for pointless shits and giggles, I wouldn't do activity X in a venue that would cause others that pain.
Now, if I was writing a satire of a religion that most of its own adherents fail to critically grapple with (i.e. The Satanic Verses, The Testament of Mary), I would be more comfortable with my
reason for causing others pain.
Basically, context goes a long way. Blackface can work in America even, with stuff like Tropic Thunder or the Lethal Weapon episode of It's Always Sunny, because there's a critical reason for its use; nobody pulls up Louie CK on saying nigger because when he does there's no doubt in your mind he's using it to make a very human point. I suspect there wasn't much thinking involved by the people at this party though.