I don't think the social ramifications of this scene would allow it to hold up. Haruhiko would just get busted for sexually harassing Mitsuru *and* the Computer Club president. There's sort of a double standard across gender lines necessary for the blackmail to work.
Japanese kids seem to go pretty far when it comes to these things, what with the infamous kancho practice and I've heard several stories of kids being obsessed with trying to grab the balls of foreign teachers. I actually find this kind of stuff fairly believable, and one of the funnier elements of the Haruhi genderswap universe.
tzimisce said: The computer club president is a girl?! This could not possibly happen!
Laugh if you want, but the president of our local computer club used to be a girl. (As in "the person who used to be president was and still is a girl", not as in "the person who is the president used to be a girl"....)