He felt his heart break in two. That is, if it hadn't already broken in two. Maybe now it was even in four pieces. It was his fault for letting the words get to him, but it just struck him as wrong.
You don't even have to date me. Mars felt terrible. Of course Priestly didn't care about any of that. He was a filthy homosexual whore and Mars had, for a time, felt like a relationship between them could have worked out. But he was so wrong. First, Priestly cements the fact that he's supposed to grow up and have a family, and now he mentions that they don't even have to be dating in order for Priestly to touch him however he wants.
He felt so terribly betrayed, but beyond that, and most importantly, he felt lonely. He thought he knew Priestly. But he didn't. Not really. Now he felt so alone, as if he had lost the only friend he knew, even though that friend was standing right in front of him.
Mars slapped Priestly's cheek.
"I hate you!" He said angrily. "I hate you so much and I'll always hate you, too! You're a stupid, disgusting, filthy human being and you're the scum of the world!"
He wasn't even entirely sure why he was so angry anymore, he just was.
"I hope you die and I hope you die soon because you're stupid and ugly and I hate you!!" He shouted and when he finished, he turned and he ran to his room.