Drawing parallels between mediums like TV/Film is problematic because there's never been anything like the internet in human history, that being said a TV example of the kind of content that shouldn't be legal: 30 minute produced broadcast dedicated to sharing fake crime stats about Muslims and encouraging viewers to organize violent attacks on their local mosques - this is what goes on the internet. Users from 8chan were (and still are) encouraging and validating the NZ shooter. We have specific incidents and shooters we can point to now. Elliot Rodgers (Santa Barbara shooter) was an active redditor and incel and had his extreme beliefs were both validated and enforced by that community before he took action, ending innocent lives. One could make a case that without the wide ranging communal support these psychotic individuals wouldn't have been emboldened to act on their hateful beliefs. Nothing even close to this is broadcast to a wide audience anywhere but the internet and it shouldn't be permitted on the internet either.
Relevant comment from HN in 2017: taurath on July 19, 2017 [-]
If 20 people were to stand up on a soapbox with a megaphone in times square screaming about /r/redpill, /r/fatpeoplehate, etc concepts they would be removed if legal, and if not legal a huge countermovement would appear to try to force them out. On Reddit you get both the megaphone and the safe space, but are still just as easily accessible to the public as anywhere.
Its "real" freedom of information, without many of the mechanisms that larger society uses to fight back against it. Instead it is just ignored and left to fester and grow until it pops into the public forum at the point where huge efforts are required to fight it.