But he's an adult and it's none of my business.
I know him through sport, he plays for a rival club but there's quite a lot of overlap, we're at the same competitions and social things.
He's mid 20s, but seems a lot younger in his manner. I don't know anything about any diagnosis, but I'd guess there's some autism and MLD. He's a nice lad, if socially awkward and often makes a beeline for me and DH because we (especially DH) make an effort with him and show some interest in his sporting achievements.
His own club is not one I'd want to be part of. It's run by a middle aged "ladies man" and has, IMO, a very laddish culture, but they're our rivals, so I would say that.
Some of the more influential people at that club "banter" with him about sex, his sexuality and not having a GF. They encourage him to say inappropriate things and share inappropriate images. It's supposedly all a bit of fun, but it doesn't seem that way to me. He has occasionally complained to DH that they "wind him up", but mostly laughs along with it.
If it was a child, I'd think it was bullying and exploitative, and it probably is in this situation, but he's an adult, albeit possibly vulnerable.
As I said, not really my business, would you 'do' anything?