Bad accents are just part and parcel of D&D, aren't they? I mean, I've done a southern drawl for my PC with people from the deep south at the game table before, if I got any indication that they had an issue with it I would have just discussed it with them.I'm curious why you feel mocking European accents is acceptable but not other ethnicities. Keeping in mind that exaggerating accent was a huge component to stereotyping Irish, Italian and Scottish immigrants as stupid, dehumanizing Germans during the World Wars, and perpetuating the notion of smug British and French elitist stereotypes.
It would be one thing to say "don't do bad accents of any culture as a joke" or "when goofing with my friends any accent is funny since they know better." But having two sets of standards doesn't fix anything,
Sorry, rant over.
Besides, if anyone ever complains about my bad Scottish accent (which, much like my French accent that's based on Pepe Le Pew) I just explain that it's not a Scottish accent. It's a dwarven accent and it can sound like anything I want.
If every time I used an accent it was for a stereotyped caricature (always using Appalachian accent for stupid people for example) it might be an issue.
But this is pretty far off topic, just rambling a bit.