Doesn't take but one rotten apple to spoil the whole bushel.
We have a weekly event here, unofficially known as "cars and coffee", technically not even weekly but people do seem to show up every week so long as the weather is decent. Always calm, and local (Maryland Heights) police often show up and chat with fellow enthusiasts (several officers are "car guys").
I think 99% of everyone wants it to be good. Alcohol is always suspect when you hear about large groups of people getting out of control.