If a dremel tool, Gojo, and/or X-acto knife is used, I agree with you. If a "salon" is involved, I would assert it is decidedly, "un-manly."
I suppose there’s really nothing wrong with it, although I can’t help but cringe whenever I see a man with professionally manicured nails. In fact, it recently prejudiced me against using the services of a potential financial advisor who preened himself and flashed his highly buffed nails in front of me. Joe, in retrospect, he reminds me of Charlie Gimbert. :-)
LOL!