I remember a friend telling me a kid threw an near empty coke can out a car window and knocked him off his road bike. The kid thought it was funny. My friend is 6'-3". But a bike traveling at 25 mph sees a denser object than a static piece of hollow aluminum. I'm sure a snowball would have been just as effective.
Forget the dangerously situation that represents on the road for a minute and think about the mindset that thinks this behavior is OK.
Nowadays adults act like children once did. Sports fans are sometimes the worst. The whole mob mentality is awful. I played football in high school and remember how cultish team politics can be. It really turned me off to a sport that I truly loved.
Where are the adults?