If someone came to your house and knocked on your door telling you to
stop your kid from vandalizing the sidewalk and making the street look like
a trash can, what would you do? You can spin it a hundred ways but it's still wrong.
Seriously, quit starching your underwear. If you get bent out of shape about kids playing with chalk on the sidewalks - something that either disappears in the next rain or can be hosed off - you really need to re-examine your attitudes.