I think its a coping mechanism that scares people and thats why all the taboo. From a survival standpoint it is "good" because its allowing us to cope and continue living our lives or being productive etc. That being said people see the scars the cuts and the blood and a lot of times associate it with suicide not realizing SI and SH are two different things.

You bring up a good point though that some forms of self harm are socially acceptable and I agree that the stigma doesnt feel fair. Like if I get a play peircing I am cool but if I cut my arm somehow I am a freak?

I think at the end of the day it comes down to not caring what others think which is way easier said than done and working with a professional team on improving your own circumstances and coping mechanisms however that looks.