While Bruce believes that Tony won't intentionally hurt him, if something goes unintentionally wrong, one or both of them has a much greater chance of getting stranded on Sakaar.

He comes close to just tapping out, refusing to go, declaring this all a stupid, reckless, insane idea. He doesn't, and it's solely because of the tired, worn down man who'd been sitting across from him in a living room that had clearly been used as a bedroom lately. If he taps out, he honestly doesn't know if that'll be the straw that breaks the camel's back, or just one that'll be counted among many when the day comes that Tony finishes breaking.

He just can't do that to Tony. Won't do it.

"We aren't getting involved in any wars, no revolutions, no reordering of a corrupt system. We're there for a break, not more of the same."

And he's never ever said that to himself and then gotten involved in something he shouldn't. No. Never. Not... once.

Are his pants on fire yet?