Scooter turns the temperature in the office down by turning the dial on the thermostat to the right. Turning a thermostat to the right would raise the temperature, not lower it.
Gonzo says that he should learn to speak French in case he is shot to the Canadian side of Niagara Falls. However, Niagara Falls actually lies between New York and English-speaking Ontario.
Scooter says that, because it is so warm in the office, he is going to "turn the AC down." AC is what makes it cooler. By turning the AC down, he would be making it warmer, not cooler. He meant he was turning the temperature or thermostat down, which would turn the AC up.