"Mocking" is your word, not mine. Granted, I did use the word "terrible", but I didn't mean deliberately so, just accents of low quality that wouldn't fool anyone and are likely based on stereotypes rather than actual speech patterns.
It's a power thing and a connection thing. Non-whites in the US have been, and continue to be, marginalized, discriminated against, and culturally appropriated for quite some time. I'm white myself, and have little personal connection to other cultures outside of Europe. Like many Americans, my heritage is European . . . and it's hard to get more specific than that. I feel as equally connected to England as I do France and Germany. So . . . I'm okay giving accents of cultural groups I feel connected to a try, and that aren't currently discriminated against strongly in the US.
It's like sports team mascots. Is it okay for a team to be named the Redskins? Is that different from the Notre Dame "Fighting Irish"? The Irish used to be discriminated against in the US, but aren't really anymore. Native Americans, very much still a marginalized group.
I'm not as far from
@doctorbadwolf's view on this as it might seem. I think using accents at the table is okay, even if you aren't trained in language and dialect! But I think you have to be careful, even if it's just with your local group of friends in your living room. It's easy to perpetuate racist tropes without even realizing you are doing so. Where exactly should the line be drawn between "okay" and "not okay"? Eeesh, that's tough, and somewhat subjective.