Suzannewithaplan - Re: porn and its harms/benefits. My answer is going to be part personal (no getting around that, as you'll see) and part professional.
I think most porn is at best boring, and, at worst, harmful and exploitative. Though there is porn out there that I do feel is changing that. I will not dump porn into one amorphous category of "bad" even though the majority is, imo.
From a professional perspective, whether you agree with porn or not, it is having a huge impact on sex on all levels, not just the physical. I work somatically with porn users who have nerve damage, and the specific approach of the kind of bodywork I do is to change entrenched, ingrained, mindless neural pathways that basically shut down a porn-mastubator's sensations/feelings/thoughts/awareness of themselves and others. Porn, typically, reduces a user to a single, well-used kind of action (think the death grip), which cuts them off from everything apart from that one, contracted, limited and limiting act (limiting in myriad ways, an example of which is cutting them off from intimacy with another person, frequently a partner who has no idea how to get through to them). A lot of this is shrouded in shame, which adds complexity to what they are facing.
I really haven't covered everything here, let alone done what I have covered justice. But that's the gist.