It's kinda fucked up but yeah the cop was right. Especially considering the hysterical behaviour of those people. American police is often very wary of raving loonies, drunks, crackheads and John Rambo's with enough guns-n-ammo in the back of their truck to start WW3. They were careful. On the whole I'd say they were both wrong, though. The couple for speeding that much and being all hysterical instead of trying to explain rationally, the cop for, well, being a fucking jerk.