I am an agnostic and find nothing humorous about this. Somebody's Momma ought to be tearing the hide off their backside, or should have done it more when they were kids. This is just simply a terribly disrespectful and crude act by uncivilized punks.
would it have been any better if done at a town meeting? yeah sure, someone should get a whooping, but kids (even good kids) sometimes do dumb things.
Hate crime? terrorisim? nah - prank? yup - no-one got hurt, local law enforcement got to blow stuff up, as far as I can see everyboby should be happy.
You are right. There is nothing humorous about this. The persecution of the Jews in Europe probably started in much the same way, a little bit at a time. Christians next?