Peter is bristling with irritation even before Tony finally makes the suggestion. Peter was trying to help. He knew that nothing he did was going to change anything. He knew they were both going to be stuck here for however long the powers-that-be decided to keep them here. But he was still trying to help, because he thought it might help Tony.

And maybe if he helped Tony, Tony would find some reason to keep him around.

"This doesn't have anything to do with Liz," he snaps. "So don't even suggest it. You want to spend more time with other people than you do me? Fine. But I've been here far longer than you have, and there's plenty of stuff that I know that you don't. So don't act like you suddenly know more than me about anything."