I didn't have to deal with this because the X cut himself off from all of our friends.
Ditto for me, but I will share something stupid that I did..
Soon after D-Day, STBX posted the video "Love Song" by 311 on Facebook with a post saying, "Don't take for granted all the good things in life....lose your head..lie cheat lose ur wife...suffer the consequences of the pain you've dealt...rise up better your self try to fill the holes of the hearts you've broke...strive for the greatness one felt..i love u Butterfly." (This was all bullshit of course because he was still sleeping with the MOW.)
A couple of days after that, a mutual friend sent STBX a text with a picture of a girl in a bikini jokingly asking him to come to a bar for some type of stripping contest. As STBX is a very bad drunk, most of our friends know this, and I thought my STBX had outed himself with his post, I thought this was very disrespectful of the mutual friend and immediately unfriended him on Facebook and a lot of our other mutual friends. I was in shock and shell mode and wanted to get rid of anyone in my life who might have known about the affair (I had no idea who knew and who didn't), so I just went nuts and unfriended tons of friends I shouldn't have.
Turns out mutual friend had not seen the post, had no idea about the affair, and was very hurt I had unfriended him. He later apologized for the text, but of course I can see how he did nothing to hurt me on purpose, but he understood how it would hurt me at the time..
I have since re-friended almost everyone and apologized to them for doing that in the first place. I was just lost and scared, had no idea who knew and who didn't, etc.. To my knowledge, turns out only one mutual friend knew about the affair..
All of these people have since told me what an ass he is, that of course they would choose me over him, and that they couldn't believe I stayed with him for so long given the way he treated me (but didn't want to say anything at the time because it was my life).
Also turns out STBX doesn't give 2 shits about being friends with any of them anyway. He's in unicorn fart land with his 2 (maybe more?) stupid naive sluts right now.
About 2 months ago, I actually woke up to texts from one of his best friends (who is an alcoholic) where he was saying he was so drunk, he needed to stop drinking, he doesn't want to live anymore and wants to die, really scary stuff. He was not answering his phone, so I ended up calling the cops to go check on him. He was fine, just hungover, and he's been sober ever since (yay!). But I had called STBX that day and told him he should probably reach out to that friend as he could probably use some support, and STBX never did. He's been such an ass to everyone.. (This seriously hurt that friend that STBX didn't reach out).
I'm actually a little sad to see how many of my friends and family are still friends with STBX on Facebook (I'm not, but his profile is open, so I can see everything). My sister-in-law had warned me that her ex had started posting a bunch of crazy shit on Facebook about her, so I'm hoping the people who do stay friends with him are just keeping a look out to warn me in case that happens.. He probably posts about 5 to 10 things a year, so it's not like being friends with him on Facebook means much..
It does hurt when mutual friends choose the cheater (just as it hurts when my STBX-in-laws support him given what he did to me), but hey, then those people just get cut out of my life, and I be sure not to tell them any personal information. And I keep things very vanilla on Facebook so that nothing can really get back to him.. Just funny videos, stuff about the kids, and I "like" and "comment" on a lot of other's people stuff to keep in touch..
I still feel bad for what I did to so many friends on Facebook, but I'm so happy that they are welcoming me back, because there's nothing like have a great support system of friends when going through such a tough time.. I still keep his family on Facebook too, and most of them are still very supportive of me and love me, and there's kind of an unspoken rule that we don't discuss STBX.. As I said before, he cut himself off from a lot of people (including being an ass to his family), so it's been very easy to stay friends with almost everyone..
But yeah, if they are still going to be friends with him on a personal level, such as planning a lunch date, that person is NOT my friend anymore, Facebook or otherwise..