I haven't yet watched this but I've heard a lot about it. I read a lot of the debate threads on the BBC news website and I noticed how, in the space of an evening, the majority went from banging on about how we need to reduce our carbon output, to believing that this isn't a man-made problem.
Aside from the bias in the do***entary that vegy has already addressed, I just generally find this sort of thing irresponsible. No matter what people like to bang on about on the internet, there are many people who can't really be bothered making changes (me included). If these people are handed a convenient little excuse to keep living the way they are living, they'll eat it up (well, I don't but clearly many do). It doesn't even need to be plausible or scientifically correct. It reduces the whole guilt factor: people will lose their homes, their descendents may struggle to survive, animals will struggle as their habitats change, etc. Yay! It's not my fault!
I usually feel that it's only a good thing that people can have the opportunity to see and understand both sides of an argument. But the anti-GW theorists have always had far too much airtime anyway. It's only recently that people have really started to accept that this is a problem, people's attitudes were changing for the better, and yet do***entaries like this will get made and broadcast and all progress on the matter is effectively lost. It's totally disheartening and, as pabs says, like hitting your head off a brick wall.