I have no real paranoid concerns about the government, but do feel that visual keys that you might own property of great value, such as guns, is not a great idea to advertise. Neither are stickers that advertise other valuable things like, "American Jewelers Association."
The other aspect is one I consider personal preference. I have no wish to debate guns with any of my neighbors who might be anti-gun and who might see such as sticker as an invitation to debate. I don't do religious stickers for that reason either.
I am also not a big fan of carrying a gun concealed but wearing a hat or shirt that says, "GLOCK" or "COLT" or some other notable gun brand name when I am out and about around town. I don't mind wearing such stuff to the range, but otherwise I don't think it prudent.
I find it funny how people claim photo vests scream 'gun' and they seem to only scream 'gun' to gun folks. "GLOCK" or "Kill them all and let God Sort them Out" with a picture of a gun seems to scream "GUN!" much louder and to a much larger audience.
Just a thought, but if I am a bank robber entering a bank and wish no troubles and I see a person wearing a NRA shirt, GLOCK shirt, at t-shirt that says POLICE or SWAT on it, you can bet that if I decide to shoot somebody, it will be the folks who identified themselves to me as being the greatest potential risk for having a gun and probably knowing how to use it if given a chance.