Something else to be considered.
To me, bumper stickers are like putting antennas on APC's. Easy enough to do......just a lot harder to take off but in any event, they can be used to influence the thoughts of the enemy and confuse them.
In the Viet Nam War, a commander foiled the enemy from attacking the command APC, because it was loaded with antennas, by putting extra antennas on all the APC's.
If all it takes is a bumper sticker to make someone give a car undue attention, then doesn't it stand to reason that the bad guy will put them on his decoy cars while the main ones don't have them?
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("You're to run blocking when we do a moonshine run. When the cops come up, you get in the way from them catching us."––the crook to the hero in some white lightning, probably a Burt, movie, (w,stte))