[Uuugh but that doesn't matter! The universe exists! You can't go back and say you really could have stopped the bomb if you'd wanted to and expect people to be impressed after it's gone off!

Ford's expression as he listens is a little hurt and deeply unimpressed, a combination that's usually incompatible, but not for Ford Pines. Angrily:]

And I'm tired of chasing you! We may have both ended up on this boat, Bill, but our circumstances couldn't be more different. At least when I get out of here, I've got someone to go back to. You're still just as alone as you were when you didn't bother to stop the creation of the universe.

[To an uncaring being trillions of years old, it is not the punchiest comeback. Bill will probably laugh it off as the evolutionary weakness of a social animal. Whatever. Ford's mostly saying it for himself, anyway: it helps to remind himself of what he's here for, what's waiting for him, what he has that Bill doesn't.

...but yeah he totally just weaponized his character development and the things he loves most in the world in an argument. Ha ha, Bill, he's happy.]