My best friend's recent ex just sent me a message.

My best friend broke up with her boyfriend earlier this week. They're polyamorous, and boyfriend was jealous of how best friend was treating a new partner. Best friend had been telling me for a little bit that her feelings were diminishing for boyfriend, and that she had been holding onto some resentment from an earlier rift between them. This week she called it quits while also trying to move her new partner into her house.

Yesterday, the ex dms me. He asks me about her past exes and recent dating life, and if she discarded them like she discarded him. The thing is, I see where he's coming from. She has gone through a lot of partners this year. There is a recent pattern in friend's dating life where she 'attempts' to date two or three people at a time but ultimately winds up breaking off any other connections to focus on whatever's new to her. We've been friends for three years and this isn't characteristic of her as far as I know, it only started after she broke up with her long term nesting boyfriend earlier this year (for a new guy.)

I love my friend deeply but I don't necessarily condone her recent behavior, and I don't think her ex deserves the treatment he got. I'm unsure on how or even if I should respond to his message because the pattern he's recognized is real, but I'm not about to talk badly about my best friend with her ex. Do I ignore it or shut him down? Do I attempt to let him know that I see the same thing hes seeing?