I totally agree with this. Birds that are properly acclimated will do fine, assuming they have adequate access to shade, water and ventilation. I keep a large black rubber pan of water (Fortex brand feed bowl, from the feed store) in the coop/run for them to stand in. I just dump the dirty water in the run when I change it out.
Artificial cooling has a way of breaking when it is needed most, and then the birds are really stressed because of the sudden change. They have a much better chance of survival if they can acclimate slowly.
It helps if you have birds from local breeders. They are more likely to be resistant to common local diseases and better able to handle local weather conditions.