it would be nice if you say what site you mean so that colleagues here review the truth. that way you can save friends who try gambling sites that you mean.
here you cannot be fully trusted if you do not show any evidence, even if you make several lawyers handle your case if there is no valid evidence I think it will be a waste of time.
Indeed. He should tell the name of the site, so we could help him to make some valid proof that the gambling site he assume that is cheating is true. Instead of calling a lawyer first, he should definitely ask help from other people to make a valid evidence, so that his accusations would not be too embarrassing.