Anyone who has to live in a fairly closed system (i.e. this planet) in which fossil fuels are burned for power would be beyond a fool to not strongly prefer gas over coal seeing as their greenhouse emissions are close enough to be within arguing distance. It's all the other stuff coming out that's the problem with coal.
I think the point is: "you'd be a fool not to prefer gas, because while the greenhouse emissions are about the same, for everything else coal is much worse"
They said gas over coal. If you accept the claim that GHG emissions from gas and coal are roughly equal, their claim is the other pollutants from burning coal make gas far more preferable.
If their greenhouse emissions are even close only a moron would not pick gas over coal because the former's emissions lack all the other nasty byproducts that are present in the latter's emissions.
Anyone who has to live in a fairly closed system (i.e. this planet) in which fossil fuels are burned for power would be beyond a fool to not strongly prefer gas over coal seeing as their greenhouse emissions are close enough to be within arguing distance. It's all the other stuff coming out that's the problem with coal.