It's the same exact thing where YouTube is promoting pedophilia. These systems are content agnostic and will give you what it thinks you will click on. If somehow people really really liked videos about the number 27, then if you click on one video it will start showing you more. It seems to me that it's a fundamental part of what these systems are. It's nigh impossible to say "do this but keep the bad stuff out" unless you have human moderation. I'm certainly not saying these companies aren't culpable. It just seems weird to talk about individual cases in abstraction like Instagram is going out of it's way to promote self harm.