Why the disdain for environmentalists?

As an unabashed environmentalist, I see this sentiment echoed pretty often. It just so happens that I saw two cases of it in the past few days. First, there is the Alabama congressmen who said, quote:

"We hunt liberal, tree-hugging Democrats, although it does seem like a waste of good ammunition."

But worse than that was Limbaugh's newest response to a study promoting sustainabilty through better access to contraceptives to prevent "70 percent of unwanted pregnancies". First of all, why would anyone be for unwanted pregnancies. Second, why the extreme language over something that seems like a pretty common-sense idea. Limbaugh's actual response to the reporter from the NYT's who reported the article:

"The environmentalist wackos are the same way [as terrorists, from earlier]. This guy from The New York Times, if he really thinks that humanity is destroying the planet, humanity is destroying the climate, that human beings in their natural existence are going to cause the extinction of life on Earth -- Andrew Revkin. Mr. Revkin, why don't you just go kill yourself and help the planet by dying?"

The thing is, environmentalists feel just as strongly about protecting the country as the far right - they just have different ideas on how to go about it. I hope that once we get over this conspiracy theorizing about the far left's desire to destroy all that 'real Americans' hold dear, we'll also realize that environmentalists are people too.