Because those are what Americans think they believe in, not what they actually believe in when push comes to shove. You overthrow an American-aligned tyrant and you're suddenly a terrorist, the wrong people wield guns and they're suddenly taken away (see: Black Panthers) and I'd certainly like someone to tell the prison-industrial complex about the liberty stuff. Americans like to call these "American values," but if you care at all about these values and take even a cursory look through America's history and at its modern states, the only logical conclusion is to hate America's guts. Therefore, being un-American or anti-American says nothing about one's disposition towards tyranny or liberty.

I'll let you know as soon as we actually overthrow our tyrants and establish liberty.

Because the tool of oppression can also be a tool of liberation. Because the power to take a life is also the power to save a life. Because with power comes responsibility, and if people cannot handle that responsibility then we as a society should not be granting them that power.

I can in fact be in favor of both the right to own firearms and the use of legal controls on firearms. If you can't understand that then I'm afraid I can't help you.