Even child porn isn't an easy subject. Everyone can agree that liking 12 year olds sexually is pedophilia and images about that are child porn. But when we are taking about 16 year olds it's muddier since we are taking about child porn outside of pedophilia.
And that's just (north western) Europe who are culturally very similar to the US.
It's not muddier. The issue isn't the nature of the people viewing the content, but the ability of the victim to consent to the creation of the content. There's no muddiness involved here - sexual exploitation of minors for the production of media is not ok.
For 12 year olds it's much easier with the "we don't support pedophilia" argument (which has wide support)
I'd rather see nudity censored than criticism of religion, to be honest, so thank the Lord it's not Europe using soft censorship.
In the latter case, is child pornography probably indicative of a crime? Absolutely. But banning the images and their dissemination is clearly an infringement of free speech. In the former, banning hate speech is also clearly an infringement of free speech. If someone's actions result in violence or death then punish them after, and divorced from the issue of speech; do not place prior restraint on speech.