Similar to this question, but I feel the context is different enough to warrant its own question.
Here's the question first, with context to follow:
What can I do now to bridge the professional gap with a colleague who is dead set on giving me the cold-shoulder caused by the callout of their immature behavior in a non-work context?
I'm a gamer and I like to play MMO's (massively multiplayer online games). I'm the leader of my in-game guild - as such, it's chiefly my responsibility to police the behavior of guild members to ensure that they align with previously agreed upon standards. There's a no tolerance rule for some behavior that I believe to be unacceptable, and nobody is exempt from it. Up to this point, this has created a cohesive, focused, and functional group who enjoy tackling difficult content together and are experiencing no small degree of success. I consider myself to be a subpar and uncharismatic leader, so I take great pains to seek out opinions and strategies from my guild mates and commend them on progress and improvements made. I really try to make things positive and fun so that we'll keep meeting up and continue experiencing new content together.
I invited a co-worker to join us, showing him our guild charter first and ensuring that he'd be comfortable with conforming to those rules (essentially, don't be a bigot) and accepting my enforcement of them. While he is senior to me on the org chart at work, he doesn't have any authority over me - we're essentially peers, so this doesn't represent a power dynamic reversal or anything. It was a gesture from me to include someone who outwardly appears pretty unhappy and lonely into a social context.
The co-worked stopped by my cubicle at least once per day to get a primer on what he needed to do to catch up. I offered strategies and the paths that I'd taken in the past to attain the degree of success that I have. One such path is pursuing "rare hunts," which are enemies that are available during a short window in a random location and require several players to defeat. Typically, you have between 2 and 5 minutes to reach the location and engage the enemy before it's already been defeated. He asked for me to share announcements of discoveries of these enemies so he could participate.
A few Saturdays ago, we had this exchange, verbatim, via in-game text chat (CW - coworker, SD - sleddog):
CW: people are total assholes when it comes to hunts
SD: I dunno, the fact that they share the information instead of taking the kill themself indicates otherwise.
CW: and when they kill it when people are still on the way. I'd rather not have the carrot dangled in front of my face. That's kind of a douche move
SD: hunts aren't something you can do casually. You're either ready and waiting for them to drop, or you're in an instance/gathering/crafting
CW: if that's the case and it's so hardcore, then why bother spamming it out to the casuals in the first place?
SD: Dude, I really don't want to make things awkward, but stow the negativity.
He didn't say anything beyond that. Upon finishing up what I was doing, I checked the guild log to discover that he left the guild, our Discord server, and our WhatsApp group chat. Which is fine - really, no big loss to us at all. Several other members had already complained about his serial complaining and negativity. I value my group's cohesion and success above emotionally coddling a grown-ass man who doesn't know how to get his stuff together over a videogame, even if said grown-ass man happens to be a co-worker.
Now, however, he is enacting a staunch no-communication policy, made more awkward by the fact that my cubicle is adjacent to his. He doesn't return any salutation at any point, even going so far as faking a kidney stone attack to avoid going to a birthday event for me and another co-worker in our department. The kidney stone attack isn't improbable in and of itself - he has them often. As a serial complainer, however, these never go unannounced, and an "Oh uh...I uh...can't because...uh...my kidneys hurt" doesn't fit the pattern of colorful descriptions of the agony of a kidney stone.