I say, Australia's Labor Party seems to be a bigger risk of harm towards youths than anything else.
Not that such a ban would actually be enforceable; when you tell young people *not* to do something, they will do it even more.
The young are generally tech-savvy and know how to circumvent internet censorship. The only way to really implement such a ban would perhaps be requiring photo ID to use such sites, but you could use a VPN for instance, accessing it from a country that has no such laws.