I don’t think most anyone argues that CO2 functions in that manner. 50% or more of the greenhouse gases in the atmosphere is made up of water vapor. A slight increase in one greenhouse gas, CO2 for example, would cause a slight increase in the Earth’s average temperature. This slight increase would cause an increase in water vapor in the atmosphere due to evaporation which would lead to an increase in temp which causes more evaporation and on and on. Conversely, lowering CO2 levels would cause a slight decrease in temp which would lower evaporation which would cause a decrease in water vapor which leads to more lowering of temperature and so on and so on.
Any thinking person. But there are a lot of them out there who eat crap like that up.