Now that you mention it... it's difficult...

I accidentally got into a toxic hobby group. The whole situation mirrored a far more dangerous situation from my past. It took a while to see it for what it is and to get out of there. The anger I felt is what got me to understand trauma and IFS.

A friend who was also in that group helped me with the emotional aftermath. We helped each other see the toxic mechanisms of that group: Gatekeeping, gaslighting, manipulation, lots of bad things. The friend witnessed how much suffering it had caused. Not jsut for me but for other people in that group too. I dropped the group, he stayed.
I am fine with him staying in that group or meeting those people.

However recently the friend calls a person from that group who had been a direct gatekeeper to me. Gatekeeper downplays all situations and badmouths me. The friend stays neutral. He also doesn't affirm that he's on my side. He doesn't make time to help me calm down.

We decide to not talk about this group again.

The calm part of me says I can not dictate my friend who he meets or what his opinions should be, but Wild Child say that I need friends who are on my side.
I ask two other level-headed friends: One friend says to drop him because it's better to have quality-people in my life, one friend says I'm controling or self-isolating.