Ok, so my apologies if this comes out kind of long and sort of complicated, but I want to make sure I put in all the details and leave nothing out.
So, my FI and I had figured out the pairings we wanted to do, and we decided to put John and Sally (names changed) together, because we thought they'd get along, though with no matchmaking intentions at all.
Anyway, we went out to dinner one night, with John and FI's brother and FSIL (his brother is getting married shortly after us), and I told John, in passing, that we had paired him with my friend Sally.
The next day, John sends me a message on Facebook asking if I minded introducing him to Sally via FB, just so that it wasn't a totally blind meeting the day of the wedding. I thought it seemed like a little bit of an odd request, but it seemed pretty harmless to me at the time, so I asked Sally if she was ok with it, and then connected them via FB.
About 2 days later, John sends messages to my FI and me, asking if we're ok with him pursuing Sally romantically. I called Sally to check and see if she was interested in him, and she said she wasn't, so I responded and told him that, while it was great if he wanted to be friends, she was not interested in a relationship, and so anything romantic was out of the question.
This is where I realized I had been an idiot. John was on the rebound from a really nasty breakup, and started sending her messages CONSTANTLY. The messages would say things like, "I looked through your pictures, and I think you're very beautiful", or she would upload a new picture, and he would immediately make a comment about how beautiful he thought she was. Sally, understandably, was rather freaked out about this, and asked if my FI and I could intervene, and also if it was ok with us for her to just ignore him. We told her that was totally fine, and apologized profusely for this totally creepy behavior. My FI tried to intervene, but then John started dating someone (not Sally).
Since then, he has backed off a lot, and the last message he sent her was a simple "Happy Birthday", with nothing else. We have invited his new gf in the hopes that he won't be creepy at the wedding, and to hopefully give Sally the opportunity to enjoy the wedding without worrying.
So my question is this: if he asks why we changed the pairings (we did immediately after this all happened without saying anything per Sally's request, and then had to change it again, due to one of the GM having his leave cancelled by the Navy), is there a good way to say it? My thought was to stick to the whole Navy leave cancellation thing, and then not worry about it, but he's paired with a different BM (who's married), so just in case he asks why he was switched, I'm trying to think of something to say. Any advice?