Do you tell them how their personal choices sicken you?
You need to calm down a bit, because I'm not targeting you at all; this is a refrain that has run through this entire thread. "MY cutting is understandable, but THEIRS is sickening!" "I get it if you're doing it because you're depressed, but if it's because you feel that you don't get enough attention? WORSE THAN HITLER." I just can't imagine how people are so judgmental of the actions of others; so what if they want to be cool? People self-destruct all the time in ways that have nothing to do with you. In fact, choosing to self-destruct is often argued as proof of a mental disorder - as in, the fact that you are doing it is itself proof positive that you have something wrong in your head no matter what you say because otherwise you wouldn't be harming yourself for life simply to be seen as cool.
There's so much judgment on those who choose to self-destruct; honestly, if anything there should be more tolerance and acceptance of those who actively make the choice to cut because they want to in the same way that people pierce themselves or get tattoos or take risks; unlike those who don't feel like they have a choice, that can benefit from people helping them stop and keeping a close eye on them, these people are just doing what they want. If it ends in them self-destructing, then it's their life that's destroyed, not yours. Who are you to judge them for choosing to do what they want with their life?