This is what an immature person would do. The fact that you think this is what the majority of people who have such a bumper sticker would do, is a long distance from the truth. It says even more that you think it's 'funny'.
I don't have one of those bumper stickers. If I get pulled over, it's likely because I did something that I should have gotten pulled over for. I take my lumps and pay my ticket. Adults admit when they have done something wrong.
There have been a couple times when it was obviously a revenue generator, and it was addressed then and there, much to the officer's chagrin.