If you'd put something like. "I've slept with my cousin, it's only happened a couple of times and we've agreed not to do it again, but I'm feeling a bit worried and could do with some reassurance that I haven't done something terrible" then you would probably have got more considerate responses.
But you phrased it as if you were just wondering about people's opinions on a taboo subject, like "Is it weird to share a toothbrush with my OH?"
So you got honest, uncensored opinions. Also you didn't seem too bothered what people thought, so I don't think anyone thought you needed or wanted your feelings to be considered before they posted.