Trust. But verify. Step-father of a 12 year old boy here. We started monitoring his internet after we caught him looking at inappropriate videos on youtube. He knows he is being monitored and I only block actual porn sites. Neither of us like it but until he has earned our trust back, the situation will not change. I'm his parent, not his friend. My job isn't to make him like me, it's to raise him with proper values…
When I was 15, I discovered Usenet and the various binaries subgroups. This was beyond what my folks understood was on the PC. Your son will access content beyond your current understanding as well. Additionally, you might have a monitor on the PCs you own, but you don't have a monitor on his friends PCs either. The monitoring game is already lost. You indicate a loss of trust, but it goes both ways. There's absolute…
I often ask him for advice on how he things I should handle a situation, and after reasoning things out, he usually comes to the same or a similar conclusion as me.
He has impulse control issues, and while he needs to learn to control them, he also needs to be protected from any significant harm as a result. I'm okay if he gets burned because he touched the stove after I said it was hot. Some things he needs to learn the hard way.
I'm not okay with him getting 3rd degree burns because he was playing with a lighter and accidentally set his clothes on fire.