If you have Choice A which actively makes things worse and Choice B which doesn't make things worse then Choice A is the "good" choice as it is the one that causes the least harm. Driving a 50cc scooter instead of a car doesn't actively help carbon emissions, in fact it still puts out carbon, but it any reasonable person would say that switching from a car to a scooter helps the environment. Splitting hairs over whether doing less harm counts as "helping" isn't very productive.
If you have Choice A which actively makes things worse and Choice B which doesn't make things worse then Choice A is the "good" choice as it is the one that causes the least harm. Driving a 50cc scooter instead of a car doesn't actively help carbon emissions, in fact it still puts out carbon, but it any reasonable person would say that switching from a car to a scooter helps the environment. Splitting hairs over whether doing less harm counts as "helping" isn't very productive.