He was pissed at her even before he found out about Blair choosing Chuck.

By far,because Serena not Make him to have sex with her,but he do it a free will,is was far away from Rape.

^What. Who said anything about rape, lol.

Dan was angry because Serena got him drunk and manipulated him into believing Blair had already chosen Chuck. Also, because she schemed and prevented Blair from showing up to the party and talking to Dan. What was pathetic was that Serena actually tried to get him back the day after.

lololol Rape? what the actual??

Sorry, but:
1) Serena didn't get Dan drunk. She didn't force him to drink or anything.
2) Yes, Serena tried to manipulate Dan, but he could pretty much have said no to having sex with her and go find Blair
3) Serena didn't prevent Blair from showing up at the party. Blair had already make her choice. She chose to go to Chuck.

Pathetic to me was Dan trying to put all the blame on Serena. Dude, he cheated on Blair. It was his choice. Serena didn't force him to have sex with her.

^Agree

Well, Dan is old enough to think for himself... Serena didn't force him, he knew what he was doing.

Both

Dan needs to take responsibility for his actions for once in his life. Serena didn't force him into anything. He even went on about how him and Serena were good together after the sex, so he obviously enjoyed it.