I asked about social media though. Not a tiny subset of social media.

I ask because if social media has a positive affect on mental health overall then it cant have a negative affect overall. And I ask because I think everyone intuitively thinks that idea is ridiculous. But you can't disprove the net negative affect by looking at some subset.

I think you are saying it can be used such that it has a positive effect. I agree with that but I think it's missing the point.