McEnroe wasn't trying to be a jerk. He was trying to pay Serena a big compliment as the greatest female player ever. And he got painted into a corner by the interviewer. It hurts women's sports more than helps them in the long run to be constantly compared to men in ridiculous fashion. Women's sports exist perfectly well in isolation from the corollary men's game. Mixing them and comparing them will always be more to the detriment of female athletes than of male athletes, regardless of the intention.