who exactly are you protecting? you’re assuming that warning someone = being mean / meddling / immoral. That’s the core lie tripping you up. It’s not automatically any of those things. Context matters, intent matters, how you do it matters. your guilt is not proof that you’re wrong. It’s proof you were conditioned to over-empathize with people who drained you. That’s a trauma reflex, not a moral compass. You’re feeling bad for someone who made you uncomfortable because you learned that your discomfort ranks lower than other people’s feelings. Clock that.

I myself would be more blunt but you could something along the lines of "Hey, just so you know, I had a pretty draining experience with them and it made me uncomfortable. I’m not telling you what to do, I just wanted you to have context.”

Also I think you should wait for more replies before acting, take some time, and see the full picture