You gotta remember that Mario is from New York. Everyone acts the same way as King Koopa there. So it’s not big deal to him. Plus, it’s go karts.
and gold, and tennis…
He’s got you penciled in for kidnapping again next month anyhow.
Plus, if Bowser ever stopped kidnapping the princess, Mario would have to go back to being a normal plumber. He probably arranges the kidnappings so he can stay in the Mushroom Kingdom and eat more Toad-babies.
Mario is a real good sport. I mean, what character does forgive the misgivings of the other and invite him to play? Certainly Peach is just being jealous.
I think I remember seeing this on the TVtropes page “Go Karting with Bowser”.