[cgoddard]

For someone who's part of a group that hasn't been historically marginalized and discriminated against it's a lot easier to laugh off racist or sexist jokes regarding their own differences. With a bad historical precedent however, an otherwise harmless joke reinforces and reinvigorates past discrimination and marginalization, and actively contributes to a hostile culture and specifically a hostile work environment in this case.

Just because you wouldn't be offended by something doesn't mean lots of other people aren't, or that your harmless and thoughtless jokes aren't deeply offensive and repugnant for historical reasons you possibly haven't considered.