Why not get the 2 girls in the car

They were trying to show how far gone he is mentally. In the censored version they cut and what you want is implied but it ruins the story

--Ju know what a "Hasa" is Frank!?! Dat's a PIG, that don't "FLY STRAIGHT"

Easy one. He should have busted them for driving drunk, high, and without a license. But since he was willing to let them go, he wanted a favor in return. Since sex is out of the question during a traffic stop, he just took advantage of the moment to get his rocks off. Also, this would leave no chance of them to claim they were raped since he was on duty. That's how I interpret the situation.

It's a weird and disturbing scene. The fact that he makes one of the girls pretend he's sucking someone off while jerking off is particularly unsettling. I do wonder why he didn't actually get physical with them but I suppose they were trying to not make him seem too inhuman. Also, I think in a sense it was an exercise in control. He was a cop and used to telling people what to do; if he had just raped them it would have been more like using them rather than commanding them.