I don't think so; I believe fraud only covers financial liability. He might be able to sue in civil court for "emotional distress" and, if he plays his cards right, argue that his draft stock (and thus, his paychecks) fell because of the incident.
Can he? Not sure. But I sure don't want someone receiving money for being a naive fool. I can tell you this however, its going to be real fun for Manti, whichever team drafts him, when he gets hazed by his teammates and the Kekua story gets brought up every five minutes.
Technically because of the situation he has lost draft stock and been embarrassed. That however is partly his fault.
Technically, the answer to your question is 'yes'. Anyone can sue anyone for any reason. The question is not 'Can he sue?' but rather 'Should he sue?' or 'Would he have any possible chance of winning a lawsuit in this case?' On that question, I do not know. However, the courts seem to be a little bit more insane with every passing day, so honestly it would not be completely out of the question that he could 'win'. However, suing some dipstick who got his jollies from pretending to be someone else, well, even if he wins, what would he get out of it? The guy certainly has no money, not the millions that he would be seeking, so what would be the point, even if he could win?