What is the opposite of "green"? [closed]

The best way to complete the sentence is to rewrite it. The only meaningful English word in common currency is anti-environmentalist, but using that simply exposes how trivial the sentence actually is in the first place.

Joe has decided not to endorse environment-friendly sentiments would be an acceptable rewrite. I think Joe has decided to become an anti-environmentalist sounds odd, but maybe that would do.

Sometimes the best way to describe the opposite of doing something is by not doing it.

If Joe is just not letting it factor into the equation, I would say this:

Joe, in opposition to environment-friendly sentiments, has decided not to go green.

If Joe is actively intending on choosing the most harmful products he can find, ...

Joe, in opposition to environment-friendly sentiments, has decided to go to Hell.

;-) Kidding, sort of. Although I don't have a way of saying that.

I would go with polluting, environmentally hostile (or unfriendly), antiëcological (or antiecological, or anti-ecological; see here).

As the context is already clear, why not a more general term? For example...

Joe, in opposition to environment-friendly sentiments, has decided to go to the opposite extreme.