Carriers can't be sued for the content they carry. It's been tried many times and so long as the carrier acts like a carrier (neutral channel), it fails.

Working at MySpace and getting sued by all the state attorney generals, that defense doesn’t work. We were ultimately responsible for the actions of our users including exploitation of minors which triggered the investigations.

If you sue successfully you can get a legal order to take down the content as part of the judgement.

Libel, slander, and harassment are all crimes or civil offenses (illegal). They work pretty well.