It's a very difficult topic to talk about, especially since there's so many people like Shawkat2009 who so kindly demonstrated how NOT to reply to someone who has seen people suffer.

However, I do believe that people use porn primarily as a high to numb their own suffering rather than because they don't love their partner. Of course, that triggers a vicious cycle because in the long run regular porn use can easily lead to more pain, which in turn leads to more porn. I speak from experience. I struggle with porn, and the cycle is not fun for me.

I'd talk with your friends about this and let them know how you feel, but try not to force them to change. That's like trying to stop a train speeding at 100mph. It doesn't work.

Good luck to you.