One pulse of his energy absorbing ability would put an end to any harassment.
Not to mention that Null wouldn't get shunned. If anything, male students would probably get Null to teach them how to get a girlfriend. Think about it, new guy shows up and within 2 years ends up in a consensual, poly relationship with half a dozen women. Sure, that might be something to be jealous of, but this is the same guy who tried to take on the Juggernaut to help an injured student and to take the pressure off Colossus, who took on Sentinels to save the lives of other students and ended up in a 6 week coma for it, who fended off a mob of anti-mutant bigots...IN HAND TO HAND COMBAT. And then there was the whole event at the end of Summer. Null's probably a legend at the school by that point. He's never going to be shunned just because he got some with Storm or Dazzler, if anything, it would make him even more of a legend.