The line was uttered near the end of the movie. Ice-T plays the part of Scotty Appleton, a New York City police detective who's mother died at the hands of Nino, a powerful drug lord. Scotty confronts Nino near the end of the movie and he aims a gun at Nino and says, "I want to shoot you so bad my d*ck is hard!"
When I saw your post "Let's go kick Brady's ass" for some reason an adaptation of that movie quote came to mind, "I want to kick Brady's ass so bad my d*ck is hard!"