If you'd done that to me then I wouldn't speak to you again.

Your intentions were probably good, but we don't judge people's intentions, we judge their actions.

What you did was spill the secrets of your best friend to another group of people, so that they'd treat them differently, without their permission, without telling them that was what you did, because you decided it was the right thing to do, even though they had never even hinted to you that that was that they wanted you to do.

Your friend vented to you, as a friend and peer, and you treated them like a child. You took on a parental role and had a meeting with the rest of your friends basically saying "Hey can we all be nice to X because of all these things that X told me and asked me not to say".

Surely you can see how patronizing this was? Surely you can see how it entirely disregards your friend's feelings and opinions?

It's not your job to take care of them and it's very insulting if you to try, especially as a result of their mental issues.

I agree that you're not worthy of their trust. They can't trust you to do what they want you to do, they can only trust you to do what you've decided is right for their life. That is a shitty quality in a friend.