Didn't Sharp already try to do that and lost his lawsuit? I've only heard about it second hand but I'm pretty sure he has no legal case against iHub.
And even if he could get their names and sue individual users for defamation, would he even have a case? Truth is an absolute defense and opinions are well protected, so he would need to show that someone went too far. Didn't he try that with Jason Black and got half his lawsuit dismissed? I haven't followed it closely enough to know if he got the entire defamation suit dismissed or not.
Which reminds me, didn't he also sue Brett Rosen recently? I wonder how that is going, I'll have to go look it up.