It's more likely it wouldn't be able to handle the number of people + PCs. They are sized for use, and they may be hitting the limit with just the people in there, then add the BTUs coming off all that hardware, and you've got yourself a sauna.
I have lived in very few houses that have had aircon, if they did it was evaporative and near useless.
The house I am currently in is getting aircon installed next week.
It might be hot in Australia, but mainly we just built houses with insolation and fly screens.
It would depend on the event hall. If it was in a warehouse like hall and in spring or fall, sure you'd keep your shirt on.
If it was in a event hall with a lower ceiling, carpet on the floor and just some form of insulation it'd get crazy hot really fast. Because on top of thousands of PC's there'd be thousands of people too. In summer it'd be even crazier. I definitely remember going shirtless at some of those lans.