<human>: Can you succinctly summarize the text in 1-3 sentences?

To be brief, a long time friend of mine stabbed me in the back (spent a year hitting on my girlfriend, then took her out, got her drunk and fucked her the day after I moved to another city. I made it very clear in advance that I wasn't okay with him hitting on her or asking her out, called him out multiple times, he did it anyway then said that "there's no such thing as dibs"), now all of our mutual friends, who have always been my good friends, keep saying that they don't want to choose sides, that they like both of us, that they don't want to "rock the boat".

I want to spend time with my friends, but it sickens me to see him around, and I've been very open about my dislike of him because of his betrayal, so it's no secret. What can I, should I do?

(I know a lot of you are going to say "it takes two to tango" etc, yes I know, I'm not in contact with my ex anymore, I blame her just as much as I blame him, but I never have to see her, so it's a non-issue)
<bot>: Best Friend" sleeps w/ my ex knowing I wasn't okay with it, mutual friends acknowledge it but keep inviting him around, what to do?