They can give you a hard time about anything they want too. And worse yet, thanks to 911, if you react in a way they don't like - you can lose all your rights for three days without them informing anyone they took em.
Of course, 99% of the time they don't give people a hard time. But when they do it's a PIA as you have no power. As in none. Just smile and if you feel it's worth it - take it to court.
It might seem worse to some because as much as the computers ensure there is randomness in the "inspections," recall these people are paid to profile.