There isn't really much will to do anything about children and internet pornography. If there were, we would make the easy changes. The most obvious one is to remove pornography and highly sexualised images from the places we can control. We could take pornographic images away from public spaces that children can reasonably be expected to be present in - newsagents, supermarkets, TV before the watershed (which many tv companies don't - they just break the law and pay the fines), adverts for lapdancing venues in public places and so on. That way, when kids are on the internet, pornography hasn't been normalised for them before they come to make a choice on the internet.
Rather than try to link contemporary pornography to social ills that are difficult to research and will take a generation before we can really demonstrate one way or the other, we could act now on the problems we do know exist. Many people are harmed within the sex industry - so let's put in place better services to help those people. Many people are addicted to pornography, and that is damaging them. Let's put in place better services to help those people - we don't need to demonstrate that pornography is always damaging to admit that many people are being damaged by it right now. Many people live with a pornography addict, and that is damaging them. Let's have services for them too.
We talk to children about racism, sexism and homophobia in the media and wider society. Just because something is pornographic, it doesn't make that media have less of a psychological impact on the viewer. So let's talk to young people about racism, sexism and homophobia in pornography, and find out what they think (and tell them what we think) rather than just assume they're not influenced by it. Pornography does not have some magical power to not influence people when the rest of the media clearly does have an influence.
We can do all of these things to change our culture without trying to find some complex and implausible way of making it impossible for children and young people to access pornography online.
The situation with pornography is rather like the situation with alcohol. It is a huge industry, and as an industry its purpose is to make money; it doesn't care about the impact. Many people enjoy drinking, but the fact that they do does not erase the problems associated with alcohol. But we don't want to see the problems of alcoholism and binge drinking - it spoils our fun. So we underfund help for alcoholics and those who live with alcoholics, and brush the extent of the problem under the carpet.
It doesn't have to be an either/or situation. You don't have to want to ban all pornography and hate everything about it to acknowledge the fact that it is causing huge problems right now for some people, and as a society we could do something about that.