They have lost credibility because they make claims that can't be backed up. Unfortunately the general population doesn't educate themselves before forming an opinion. For a while there global warming was considered fact. Now fortunately there is more accurate info available, more studies have been done by people who don't have a financial interest in changing governmental policy or selling "green" products. Read up on solar cycles, it will open your mind a bit.
"environmentalists" (tree huggers) will always try to stop development and establishment, and will make wild claims to do so. I work in the oilsand mining industry in Canada, I see this and hear about it everyday. EVERY single claim made by these people has been proved wrong, but that is another conversation for another day. Take away their Biased BS "info", and they haven't a leg to stand on. they lose one fight, they pick another. It never ends. I never will until we're freezing out asses off.