Good question.
I think you got turned around in answer choice (D). I know that as I just sat down to answer it, (D) looked really good for 30-45 seconds. The problem with (D) is this
The position attached by critics of environmentalism is environmentalism. The author says that "serious environmentalism is by no means political orthodoxy." The answer choice says that environmentalism is the prevailing orthodoxy - clearly the opposite of what is suggested in the passage.
With regard to answer choice (A). The purpose of the author is to challenge Winslow. Bun in the process, the commentator concedes a point. Answer choice (A) merely states the point that the commentator conceded. So, Winslow was right about the preference of newspaper editors for controversial articles.
Let me just tick off what's wrong with the other answers...
(B) is contradicted by the passage. The commentator says that they were successful in selling themselves as renegades.
(C) is off topic. There is an issue that the commentator has with Winslow. However, the frequency with which critiques are published is not it.
(E) is an unsupported prediction about the future.