Not a problem for me; never seen the people handing them out touch a car.
Generally, if I'm near the car, they'll ask if it's mine and if it's OK to drop a flyer inside.
They're just trying to publicize their show.
I don't expect them to ask everyone around if they have a car to show.
If someone was about to palm the car or whatever, I'd get involved, but that hasn't happened since I left California.