Who's "we"?
At least here in the US, >60% of the voting public are Facebook users. So we're not talking about "a significant portion" - we're talking about the majority. You sound an awful lot like someone trying to claim that "you know what's best for us".
I think it's clear that Facebook on the whole has detrimental effects on society.
I don't think this is clear at all. Rigorous evidence please! And not "oh look this bad thing happened" - because if that's the standard of evidence then we should ban cellphones, airplanes, riding lawn mowers, and chewing gum.