I think I am less offended by people singing songs in their own accent (even if it is not the accent of the originator or populariser of the song) than I am by people putting on fake accents (good or not).

But one too good to miss: --

I say, I say, I say! How does a bee with a cleft palate sound?

...

Mzzzzzzzz!

(gets coat, wondering why SWMBO is so hung up on whether people have been properly introduced to her)