Is AUTHOR wrong in the post ? POST : I have a friend, we'll call him "B", that recently had his gf break up with him for "not loving him anymore". X was devastated and went to talk about their break up with another friend of ours, we'll call him "R". B talked with R about how he was still madly in love with her and how he couldn't bear to be away from her and all, he cried in front of him and told him his deepest feelings. Recently though, I found out that R had been getting on with B's ex in the same week of the break up. B would arrive in the afternoon to talk about his feelings and when he left, his ex arrived for the night. 

I was infuriated by this, especially knowing that they were trying to keep it a secret from everyone and that they might have been hooking up before the break up (she was visiting his house by herself semi-regularly about a month before it). Meanwhile B was still sending his ex letters and messages (nothing too crazy, things like saying how even though they broke up, he was glad he had met her and that she changed his life etc.).

As soon as I found out I called B and told him that he should stop doing things for and romanticizing her. That he'd be better off absolutely forgetting her and that he deserve much better than the scum that surrounded him (R and his ex). I didn't tell him what happened or why I was saying those things, just that he should trust me.

So, AITA for getting myself involved in a story that had absolutely nothing to do with me, partly spilling R and the ex's secret and then telling my friend only part of the truth because I don't want to get involved any further?