In a way your buddy might have done is:
He migth have tried not betray his loyalty to another friend.
One can think that he "was siding with his friend" and/or his friend wrongdoings, etc.
Many would also think, that friend #1 is dismissing your feelings about friend #3. Feelings or even misgivings, presentiment, etc.
Or still, he could be in denial, as if friends are always right, so your feelings about friend #3 are unjustified! He always will endorse or for that friend, the same is/would be true for you?...one wonders if he would stick for you as well!