This was a prank gone bad. No one got hurt (apart from a few egos). Pulling sponsorship because of that is just lame.
Don't get me wrong, I have the deepest respect for women but that doesn't prevent me from pulling (even sometimes sexist) pranks on my wife. She does the same to me and we smile at each other.
I dare you, everyone that's horrified by their prank say it out loud (and mean it!):
"I have never, ever made a sexist joke before in my life. At least not a kind that would in any way offend someone"