First I must say to the other answerers : Sean, Lexi, Buck, and Jas are all filthy perverts. They are misguided individuals who can't stand the innocent.
What you are doing is uncommon common sense, stepping in as you should ( I do it for my two younger siblings. And I have no guilt in being a firm parent whatsoever. Long story.) ( better he grows up hating you now, then you feeling guilt for not doing as you should.)
The danger here lies only in your manner of taking away his laptop, not in your principles. ( Be firm, not nagging, or angry)
And don't listen to those guys, you are on the right track. I take away all stimilation. You do not have to lecture him, or explain anything to him. He is 14 years old you can say " Dear Jim, Im taking away your computer and whatever he has. Until you are more responsible with it period. "
Porn is very very dangerous.