The Deprogram

FWIW, I was not one who downvoted you. However, I am doubtful of the claim that there's truth in what he's saying. Not because of any suspicion toward you, but because I have trouble believing there's a clear way to frame "casual sex -> negative outcomes" in the first place, much less draw more than shaky causal links. At the offset, it would be a difficult thing to observe and study beyond (limited usefulness) self-reporting. And there are problems sometimes with psych studies that are like "we studied a few tens of college students" and it turns out it's highly relative to that region and age group they studied.

On top of that, there is reason to be doubtful in general about positions that try to make scientific the taboo of sleeping around, considering the already-existing stigma it often has (is it coming from a null hypothesis place where it's trying to prove that there is no special link between casual sex and negative outcomes, or is it trying to use science to reinforce the taboo).

And as someone else pointed out, since you didn't say where you did your reading, I can't check for myself and apply these doubts to the same sources. I suppose I could do my own web searches, but I might not find the same sources and might overly focus on ones that reinforce my doubts rather than giving a fair look to the contrary.