You guys need to get over the use of "A/C" during the winter. The reason that the A/C comes on automatically in your Infiniti (as it does in every car I have had or heard of) is because it's dehumidifying the air, so it won't condense on your cold windshield.
The fogging is because of moisture, and no "anti-fog" product is going to remove the moisture from the air in the car, you can only do that by refrigeration (A/C), ventilation, or heating up the glass to above the dewpoint of the air in the cabin. If it's precipitating outside, the air that is being brought into the cabin to prevent carbon monoxide poisoning is going to be at 100% humidity, so when you put your HVAC controls on "defog/defrost" the air first goes through the A/C evaporator to condense any moisture and then thru the heater core to heat it (back) up. Whether the A/C is actually running has something to do with the outside temp and your particular car's control logic.