Why such anger directed at the OP and why such distasteful posts about cocks and banging, there is no need for full descriptions, we all know what porn is.
Try reading, the OP clearly suffered some kind of sexual trauma as a child so that is why she has a perceived over reaction, it's not an over reaction to her and I doubt it would be to any of us having suffered any kind of sexual exploitation and anyone who thinks porn is not exploitative is either thick or in denial.
We don't watch it, yes that includes a man, we prefer to explore ourselves, we don't feel the need for porn, it's boring and unrealistic to us so no, not everyone does it!
OP, masturbation is very healthy and should not be shamed, however, as someone said up thread, in private, I don't think sitting at your laptop wanking is being very private, you probably got a bit of a fright walking in on that, I would too.
You need to talk to him about boundaries and if you don't want porn in your relationship tell him, it's your choice, just like it's his, I hope you can reach some kind of compromise together.