Where is examination of the person doing the scrolling? Isn't the flaw there?
(The following applies to adults):
Ostensibly, the person should be allowed to spend their time as they like if they're engaging in legal activity. If people thought that engaging in social media was bad for them, they would stop. Are we really saying that people cannot stop using social media? Are we saying that people don't think it's bad for them?
If people can't stop doing an activity that is definitely hurting them, don't they need professional help? Do all these social media users need professional help?
What amount of time on social media is sufficient for it to have a negative effect? Is it anything besides zero?
To be meta: if hackernews is social media and social media is bad, are we all hurting ourselves?