My dad just freaked over R ratiness, should I still watch...?

the Departed. He let me see Blood Diamond, and then FLIPPED when the "f word" was mentioned, he freaked at the violence (I saw this movie before he did, but he wanted to watch it with me). Me mom let me rent The Departed and This Boy's Life, both rated R. I said I went to public school and I hear worst langauge every 4 second of my life. Violence doesn't bother me and personally, my mom really doesn't care what I watch, she said nothing "x" rated, everything else if okay. She knows my Leonardo DiCaprio obsession and she'll let me watch anything with him in it. She was the one that let me rent The Departed. I didn't tell my dad, but once I got home and got Netflix he said that he'd take EVERYTHING away if he caught me watching an R rated movie, when my mom said it's okay. I have The Departed with me now, and I REALLY want to watch it! I've been dying to watch it FOREVER!!! Should I watch it anyway, I mean, no matter what my mom DID let me rent it. By the way, I'm 14.