Besides the point really as:
1. If the gym and forum were linked, then it was okay to distribute information
2. If the gym is independent, then your gripe is with the forum, which is a separate entity to the gym and so threatening legal action with the forum will do nothing for that situation.
Also, I very much doubt your cousin can do much about distribution of information without a lot of effort for minimal return. As far as the forum goes, they can be argued that information was passed on and processed fairly. Your cousin is accused of harassing on the forum platform and a request was made by the gym to pursue and investigate harassment between gym members and an accusation of drug use. Forums might not take a bit of trolling seriously but gyms do and forums will do if a business informs them that they are the platform for the harassment and accusations. The fact that your cousin was in the wrong to start with puts him at a significant disadvantage when it comes down to pointing fingers.
Really, you have to ask: 'what am i trying to achieve?'
If its getting your cousin out of hot water, than an apology is the only way.
If it is trying to get the forum fined, then you may get somewhere but it is doubtful and not worth the money or effort.
This is fair enough. My point was I know how to advise him on a personal level. It was more a legal level with how the situation has been handled by the forum/gym owner and then the subsequent repercussions....everyone has made mistakes and are young....he will learn from it. But my point is, what if this now spirals out of further control? What if something serious happens and yet it could have been prevented by what I perceive and possibly legally should have happened with the information?!