How do you handle a dysfunctional member of a social group?

I started hanging out with a group on people a few years ago including many quality individuals who I would be loath to lose.

There is one member whom I worry about. He’s incredibly bizarre, and I worry about what the future holds for him.

Here are some characteristics:
– He is ABSOLUTELY fascinated with Freddie Mercury. He owns multiple shirts, strikes the poses, sings the songs in public, etc.
– 90% of what he talks about ends up referring to music, incredibly obscure movie quotes and scenes, homosexual sex or animal sex.
– He speaks very very softly, to the point where you have to lean into him and concentrate if you wish to actually hear what he’s saying.
– He engages in attention seeking, inappropriate behaviors that fall short of actual injury. For example, at a recent get together he snuck up behind someone there and attempted to stick his finger in their ear. After his hand was slapped away, he continued to try.
– He doesn’t present himself well. He dresses poorly and has somewhat poor personal hygiene.
– At every social gathering, he’s always the one who takes the most pictures in order to post them on FB.

He is tolerated by the group, and as it seems he has a good heart and doesn’t wish anyone harm, the group in general thinks that getting more social interaction will do him good. Everyone seems to agree he’s mentally challenged, but they deal with it.

I worry that he’s sexually repressed and attention seeking, likely from poor self esteem and an inability to express himself adequately. I hope I’m wrong, but I fear that someday this will lead to inappropriate (probably sexual) behavior that really will hurt someone.

It has been suggested to me that someone has to sit down and explain this all to him directly and discuss how his actions make others feel. I don’t know if this strategy will accomplish anything.

I would be curious to hear your opinions.

Thanks in advance