Blackbeard said: "A lot goes in to people's estimations of each other's character. How you dress, tattoos, haircut, demeanor, how you walk, who you're with, etc. It's not as simple as saying tattoos = thug."
Someone else mentioned scowling. I agree with both of them. I'm not bothered by a heavily tattooed man who dresses out of the norm, but who uses appropriate eye contact with me, maybe smiles and greets me (if appropriate) or responds politely if I talk to him first. But a man with or without tats and beard who looks angry or aloof in a hostile way bothers me. I'm happy for the former to be armed, a little more wary of the latter.
(Speaking as a non-gun-owning female in a country which is very anti-gun.)
I know the power of preconceptions and appearances - I have to work against some preconceptions others have against myself (or others like me), and I do work hard to treat people as individuals. Whether OC'ing will hurt the gun community image, I think, depends more on how friendly and sane you seem, even if your appearance may not be the norm.
Jmo.