Here's my take on it in the form of a paragraph as "you" to your wife.

Honey, here's my thinking. I think we have attracted a troubling soul into our family's friendship. Kevin is showing signs of having a personality disorder that could lead to more trouble if we continue to have him close to our family. You may find that your "fun" text exchanges to your friends are innocent enough - but they have shown that Kevin cannot be trusted. I have had words with him that are alarming that I could share, if needed, but I'd rather keep them to myself for fear his wife would hear them.

I trust you and I want no part of his interactions with you affecting our marriage. I feel that anything at all sexual that you send to your friends, including him, is thought by him as an advance and that just eggs him on to consider when and where he will work something out with you. This cannot happen. He needs therapy, boundaries and a good "growing up".

Sure I play sports with him, it's competitive. But the personal stuff isn't going to work out so I think we need to move on to other friends while he gets some help. I don't know if we should suggest help along with a "downgrade"/de-friending/shunning (call it what you will) - but it may be for the better. Left "untreated" this guy will end up ruining his marriage, screwing up his family situation or worse - hurting others' marriages.

I love our marriage. I don't like what other people think they can do to us. Can you support me in this?