1) No they don't. Not everyone here in the US owns, nor carries a gun. It's not even a large percentage of the population that even own firearms.
2) Have you actually told people not to wear a seat belt here? Besides that, the hostility you receive is due to gun ownership being one of the rights given to Americans through the Constitution. And the Constitution is held in very high regard, and extremely dear to the hearts of Americans. You will receive the same hostility is you try to refute any other declaration in the US Constitution.