What can I do about offensive bumper stickers?

There is a car parked in my apartment complex that is covered in F*** You, Mother F*****, and other F*** bumper stickers. Stuff like this usually doesn’t bother me, but there are children around, and my little sister in law comes over sometimes, and she really doesn’t need to be seeing this. Legally, is there anything I can do?
*I live in Wisconsin, so I don’t know if laws are different here.

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