I have tried to be very open with my teenager about porn. So I have told her that I wouldn't consume it personally, because of the risk that you are watching someone who is trafficked/coerced. I have told her that some female friends of mine do use porn on occasion, and that doesn't make me hate them, but that it wouldn't be for me...
She has told me she broadly shares my views, and has little to no interest in it. But I expect she either has already viewed some, (she said she hasn't seen any yet) or if not will at some point.
Teenagers are curious. It's impossible to prevent them accessing porn, realistically (most of us found ways to view it on occasion long before the advent of the internet, and imagine how much easier it is now!); so your heat bet is honest dissuasion I would think...
It kind of depends how open you are with him about sex in general? I have never had a son, so I don't know whether that makes it harder.... If you can't speak freely to him about this issue, is there a trustworthy man in his life who could?
Good luck. I really feel for you, OP - hideous thing to have to deal with.....