How do I deal with a friend deflecting their anger regarding their partner's behavior onto another person?

[Anonymous]

One of my friends's partner made a couple of questionable choices regarding someone else a while back regarding going back to another person's home, getting high with that person, and letting that person see and touch them in kind of a sexual way. I am also friends with the partner and the other party. This friend is blaming the other party for their partner allowing that. Everyone is of legal age. I personally find it mind blowing that this friend is choosing to blame the third party and calling the third party a shitty person instead of focusing on their partner's behavior and decisions that night. It sounds like to me they are actually angry at their partner for that but are in deep denial about it.

[Guy13]

Stay out of their Business as you will get trampled from both sides. They do not need your judgment or interruption as they are adults and can manage their own lives

[In_Trance]

stop hanging out with them for a while