I’m sorry, but you’re wrong. The word “truther” has been in common usage for years now, used by a great many people to describe the various “instant conspiracy” movements that keep popping up. It is not limited to a small, politically motivated group. When I use the word in conversation, I’ve never gotten a blank look, because it is pretty universally understood. That alone makes it a legitimate word, and it is not going away, even if you don’t like people using it.
If you and your friends choose to use the word that is fine. Let me guess, you only use it to describe people you dislike or disagree with.