That gets Inigo to let out a hearty laugh. Which is probably not the best response to a threat of violence, but he can't help it. Especially since he knows Tidus well enough to understand that this is the other trying to go along with the mood he's creating here, and he thinks it's a pretty funny attempt at it.

"Wooow, train, you better watch out! This guy over here knows how to break anything!" It's a joke, but one rooted in reality. Never forget the last time he broke stuff with Gibbers, okay. Inigo doesn't even want to know what Tidus could do to a toilet. "You're at serious risk here if you don't listen to our demands!"