Years ago I saw a therapist for only one session because he was awful. It was at a bad time on a particular issue that he advertised himself as an expert on.

Now years down the line, I co-manage a local therapists' group and he has joined and offered to do a workshop on this issue. I'm pretty sure he doesn't remember me. My other co-manager knows (a close friend of mine) but the committee doesn't, and there's no real way I can be like "no" for no reason. So I guess I excuse myself for that session? I can't imagine sitting through that workshop knowing what a useless, insensitive arse the facilitator is.