Whilst I agree with the general tenor, it needs to be said: global warming is one thing. Plastic is another. Moore kind of discredits himself when he suggests that plastic waste isn't a huge environmental issue. It seems obvious enough that a plastic layer bigger than some countries covering our oceans is a huge problem.
The one thing Greenpeace doesn't get right is they're dumping it at the wrong door. 90% of the global seaborne plastic pollution originates in ten rivers which are all in Asia and Africa (Yangtze, Indus, Yellow River, Hai He, Ganges, Pearl, Amur, Mekong, Nile and Niger).