The comparison is wrong.
It would be more "It is like if children were forbidden to be in a smoker room, just because they are not the one consuming".
Yes they should be forbidden, because they do not need to smoke themselves to feel the negative effects.
Even without "porn", "murdering/violence" or other controversial content that can be found on social medias, just the negative effects of doomscrolling on the brain are harmful enough.
Their is plenty of studies that describe the effect it has on attention span, memory and cognitive capacity of kids.
https://www.scirp.org/journal/paperinformation?paperid=14350...
And lets face it: Over the last 10y, any attempt to regulate the platforms responsible of that failed miserably.