It failed to be funny not just because it's an old joke which he failed to dress up with new paint, but because he undercut his own material.
"These Ubuntu top-managers are as inconstant as women often are"
Oh, God forbid, we don't qualify the assertion with "often". The statement is completely nutless because now it's not even clear whether he's saying women are more inconstant than men. Why not just leave the word out? Afraid he might offend someone?
If you're going to enter the terrain of sterotyping, you've got to march forcefully and with conviction. And you'd damn well better be funny.