Those who post that porn should be banned need to appreciate that this is no longer possible. Sure, you can censor print materials, but you cannot effectively censor the Internet. You can stop porn being hosted on servers in countries which agree to a ban, but if even one country won't play ball you're screwed. And there are loads of countries happy to host extreme porn.
As for phones.. You have a phone camera, you take a photo, you send it. There's no practical way to stop it. And loads of kids well under 16 take photos of their own bodies and send them to other kids. Or adults. Or adults they think are kids...
The only answer, for a parent, is to talk it out with your DCs. That means early for me it was 11 and frank. Very frank. The images out there are gross, and none of the commercial software which claims to be able to block porn from your family PC works. If you don't believe me, try it. Your DCs will have bypassed it in 24 hours if they're motivated.
I wrote a long post about this a month or two back about how I handled it with my DS, who was really upset by what he'd seen. He was so relieved when he realised that aggressive threesomes weren't mandatory.