Farnam
Crowds of any kind, particularly those with an agenda, such as political rallies, demonstrations, picket lines, etc are good examples of "stupid places." Any crowd with a high collective energy level harbors potential catastrophe.
To a lesser degree, bank buildings, hospital emergency rooms, airports, government buildings, and bars (particularly crowded ones) fall into the same category.
All should be avoided. When they can't be avoided, we should make it a practice to spend only the minimum time necessary there and then quickly get out.
I have investigated a number of violence cases out of emergency room situations, in particular where some security personnel, on contract with the hospital, acted in overly aggressive and unbelievably stupid ways when coming in contact with sick or injured people seeking help.
If you are ever in a position to have to go to the emergency room, always be sure to call 911 and get there by ambulance which guarantees no bothersome interaction with security or other desperate people.