There are two main components to a sexual relationship - the physical and the emotional. In general, high school boys are interested in the physical aspect, while high school girls are interested in the emotional aspect. That is not to say that the two are mutually exclusive, just that each gender tends to focus on one rather than the other.
Many high school girls are capable of becoming aroused and enjoying the physical aspects of sex, but most of them are not prepared for the emotional aspect - due in part to the fact that many guys that age are not willing to give as much emotion as the girls want - the cuddling, the "I love you beary much," etc. That is not to say that guys are incapable of it, but that some of them don't want to or can't give the reassurance and emotional support that the girls crave.
Our societal double standard says that a girl who has sex without emotional attachment is a slut, which is part of the reason why girls are often reluctant to have sex with someone who isn't a boyfriend. It's okay for Sharon to have sex with Kyle because he is her boyfriend. She has probably had sex more often than Rayanne has, but because all of Sharon's encounters have been with the same person, her boyfriend, she is not a slut. Rayanne, on the other hand, is considered a slut (as decided by the Sophomore List) because the guys she hooks up with are not her boyfriends.
Because many high school guys are more interested in having sex than having a girlfriend, the male/female goals are almost at odds with each other. If the boys don't give their sex partners enough emotional support, the girls often feel guilty for having sex.
My point in all this is that most high school girls are NOT emotionally prepared to have sex. If, like Rayanne, they choose boys who don't care about them, the girls feel used/vulnerable/abandoned. Girls like Rayanne who have sex with guys who don't care about them are often substituting sex for real affection, the theory being that if she is getting attention then she is worthy of it - classic low self esteem. Even someone like Sharon who, for all we could see, was in an okay relationship with Kyle, had some reservations about having sex, as evidenced by Jody's quotes. It's not necessarily about all guys being jerks, but rather two people who are at cross purposes.
He was a big jerk about sex, but its normal. Thats what really happens. Guys want sex... And when they dont get it, they become jerks!
Well, to quote Brian, "Not all guys." If you are dealing with someone who is not interested in your emotional well-being, then yes, it's very likely that he will be a jerk if you don't have sex with him. Despite all that I have said, there ARE nice guys who will continue to be nice after you have sex with them or even if you don't have sex with them at all.
I also dont think he cared as much about sex with her after that episode. He finally realizes that he cares about her for more then that.
I'm not sure that Jordan is quite to the point where he realizes, "You're wrong," as he does in the finale. It takes him a while to reach that conclusion. I think what does happen after Pressure is that he begins to understand that the way he has dealt with girls in the past is not the ONLY way. We don't know much about his past relationships, but based on the way he treated Angela, it seems that he expects there to be a lot of physical stuff which logically leads to sex. Meeting her parents and expressing himself were pretty big expectations - he was surprised that he had to do these things, but I think he was in the process of learning that Angela required new and different things than his previous girlfriends (or sex partners). At first they were annoying things he didn't want to do because he'd never had to do them before - he viewed it as Angela making "too big a deal out of everything" and "too complicated." Just as he learned that she doesn't like being interrupted, Jordan is slowly learning that not every girl wants the same things or can be treatead the same way.