Welcome to the world buddy. You don't meet more rude people than you do in the life of a teenager, nothing but that as far as the eye can see. I'm a teen, but I still hold doors open, say thank you when needed and the like, but generally people still put me in the rude category sometimes. Mainly because I have this bad habit of speaking my mind truthfully, and most people don't like the truth
To me, that's not acting rude, it's just that life is too short to be subtle and to be beating around the bush.