He notices how long it takes for Tony to get around to the question, and Bruce reads it as a yes. Tony doesn't trust him, or thinks Bruce doesn't love him, and this time, the gutted feeling sticks around, not being replaced by anger. What does he do with that? He can't go back in time, and Tony sees where Bruce was coming from, and Bruce sees where Tony was coming from. There's no real in between, is there?

He still thinks this mood swing is random, but Tony's in a sensitive place right now. He rubs over his face, and then steps up behind him, reaching out to touch his shoulder again.

"I don't find it hard to love you, and that's coming from someone who hasn't had any significant emotional attachments for like, six years. And then you shook my hand."

And that was literally it, the start of it, the whole thing.