I understand that it was your husbands idea...totally his decision....but down the road he may not look at it that way...
For some people...college friendships are very tight...and just like when you are in the middle of fueding family members you don't cut one off because of problems with the other...you just don't talk about them or bring them up when you are visiting with the others...
I have been in this situation...my MIL wanted nothing to do with me....said some really ugly things to me when H left...now I had never been unfaithful...it was H who abandoned his family not me....yet, MIL was mad at me?...even when we got back together she was still mad at me....I never wanted to come between H and his mother so I let them both know it was okay....I would give messages to H from her, hand him the phone when she called, remind H that he should give her call and see how things were...I understand this is a bit different then your situation but like I said some college friends are considered "family" in the context of how close they are....
They haven't been privy to seeing the OM in the way you did....and your repeating things to them would be considered biased...
At this point I think it wise for you and H to focus on each other and fixing what was broke...you are very fortunate to have a H that is willing to work on forgiveness so easily with you...
I would also suggest to H that the deal between in-laws and OM should be ignored...that if they don't bring him up you can be okay with it...that you DON'T want to cause a division in the family because of what happened with OM...
In the future they may see OM differently...if he really is a scummy guy he will show his spots eventually....then they can make what decisions need to be made at that time...
I don't think you should make family "show loyalty"....unconditional love is what needs to be shown...something that you H is willing to show you...extend that to the family as well...