Cops don't just pull people over to check for warrants - I drive all the time, and have not been pulled over without cause in the last 25 years..
Police pull over folks who they believe to have broken the law - sure they make mistakes, but I do not believe for a minute that they chased your friend just to have someone to shoot.
Walk down the street in Utah and you WILL be pulled over. They profile like no other, I can't even tell you how many times I've been stopped, and SEARCHED! They make lies to defend their illegal search and siezure, with that 'ol, "I smell marijuana" bullshit, whether I've got it on me or not! Usually not, hence I have 1 possesion charge and have been searched at least 10 times. Different cops too, they don't know me. I don't have long hair or any other 'criminal' attributes. It's not just me either.