Everyone is entitled to their own opinion on Will. Personally, I take a more charitable view of his character. I get where you are coming from. Yes, Will knows how devastating it was for Damon when he came out and he knew Jack would probably face more of the same. But Jack wasn't there to help pick up the pieces, and Jack wasn't there to see how much pain Damon was in when everyone in his life essentially turned their back on him. Will had to help deal with that, and I think seeing his boyfriend in that much pain and dealing with that much betrayal, limits how much empathy Will could really have towards Jack. Will doesn't approve, that's obvious from being so ashamed and embarrassed that he couldn't even look at anyone, but he doesn't try to stop Damon from seeking revenge and doesn't reject him, even though he doesn't like what Damon has done.
He may be guilty by association, but I wouldn't put him on the same level as Jack or Damon. But I like hearing what other people think about it, thank you for sharing!