I think that when it comes to females, you're thinking too much into things or maybe some sort of social anxiety kicks in. I'm somewhat the same way (Although I am engaged now, so I don't need to mingle with the ladies anymore). If I am in a social setting and I am talking to people I know and an attractive female (I know I am engaged, but I am still only human!) comes along, I clam up a bit. But if I am drinking, I'm much "smoother" when it comes to talking. Now I don't drink nearly as much as I used to due to the medication that I am on.
But when it comes to guys (I'm straight, just to clarify) I feel like I can be more outgoing. I guess because with guys I am not looking to engage with sexually, whereas with women, in my subconscious, I'd want to, so I don't want to make a fool of myself (Because, you know, standing silent is totally warm and friendly).
The rudeness during sex... I have no idea. What do you mean rude? Like, aggressive?
Of course you would want to talk to girls that are less attractive. Well, maybe you don't, but your mind us much more at ease because there is less on the line. Compare it to having a casual catch versus playing in the World Series. There is (In your mind) much more at stake with the more attractive person, so you fear rejection more. Most guys are like this.
Sabotaging your chances unintentionally is because you get nervous because you perceive them as more attractive. It's hard to "act cool" when you're interacting with a woman that you really want because you think much more into it. I suggest reading some literature on body language and positive speaking. Even pick-up artist books are good to read just for conveying confidence and how to open up.