I don't know. I can't say I'd be offended by something like that. I guess it really depends on how it's said. I once had a co-worker (years ago) who would jokingly call me "wop". I never did get angry, probably because I knew her and knew she was joking.
Yogi, "Thistle Arse"?

Can't say I've know any Thistle Arses. LOL
TIS