I saw people saying their read of the scene was that Clark refused to do it because he was afraid that she would be the life he had to trade in exchange for Jimmy's. I didn't think it had anything to do with him walking out on her. His attitude wasn't, "I don't care about you anymore," but more along the lines of, "I have too much on my plate right now and I don't want to lose anyone else."

She walked in right after him being told he would be responsible for the apocalypse in a year's time, and him having to bury the messenger in his backyard. He told Chloe that, and she totally blew him off to talk about Jimmy instead. I'm not apt to cut Clark a lot of slack and I think he's an asshole in the grand scheme of things, but dude was having a bad night.