Well, Cod Fiddler - I've heard you play Irish music on that there fiddle and can't imagine why you would "feel guilty" about it.

If you feel the tune and can evoke a response in whoever listens..that's all that's needed surely.
And you do, so... ná bí buartha! (don't worry!).

Personally,I like songs about the Napoleonic wars and enjoy listening to, and occasionally singing, them. I'm neither old enough to have been there nor French..but I have read widely about the period and figure I can put such songs over well enough.So do folks who've listened to me.
I'm sure the same goes for other topics too.

Regardless of accent or background, any musician may well have a passion for coal mining, fishing, farming, hunting the cuckoo or whatever and may even be more sympatico with it than an apparently more appropriate class of person.

I look forward to catching up with you again soon!
Dáithí