NTA. Tell him (more nicely than me) he’d be a fucking idiot to turn it all the way off. You’d create a much bigger problem for yourselves. Especially if you live somewhere truly hot and it gets up to the 90s or higher inside. Appliances and electronics could break. Humidity could cause mold and warped furniture. Food would spoil. Your refrigerator would work harder and take more energy. Not to mention your own health. Compromise by setting to high 70s plus some fans or window unit if necessary