Why are Global Warming Activists so Rude?

I posted a video with a young girl addressing a conference on Global Warming. She spruiks an Al Gore line and I ask the question "An example of how the scare campaign has tragically impacted on the most talented of our young. How will this girl feel when she realizes how she has been duped by people like Al Gore?"

Without looking at the vid, I get this reply from a casual peruser;
"Denying global warming is like denying the Holocaust you attract contempt and those of low intelligence"

And you just know they haven't seen the video and they are one of the global warming crowd. But this one is brighter. I respond "Except the Holocaust happened. Pollution is really a problem caused by poverty and the fight against global warming will only make poverty worse."

The penny dropped, and the reply "sorry David, i misinterpreted what the girl said. Surely we can divide our efforts? A documentary called The Burning Season touches on this issue. I apologize for my frank words, i mean it. sorry."

Wouldn't it be nice if we could talk without the casual abuse more often?