I have Rock River Arms and a 'NRA- The 2nd Amendment; America's original Homeland Security' shirts. I have never had any negative comments just pro or people asking questions- how can I sign up for the NRA? etc. My wife has a NRA shirt too.
I like the 'Don't tread on me' t shirt on the NRA site, I probably pick one of those up next.
I don't put any NRA/ pro gun stickers on my vehicles, I don't want to invite some scumbag to break my window in search of a gun that isn't there anyway.