My AGW skeptical friends particularly resent being called "flat Earthers". They see themselves as lonely voices of scientific skepticism in a world of hokum. Of course I don't agree.
In many cases, they are pretty well informed, better informed, in fact, than the average amateur "warmist", as they like to call people like me. The group I meet with have regular presentation in which they brief each other on various aspects of climate - last week's talk was on the carbon cycle. They pride themselves of believing "data", not experts.
Unfortunately, they are very selective in what data they choose to believe and take seriously. The retired biologist who presented on the carbon cycle material had a lot of details of facts and figures but the only thing that seemed to make an impression on him was the fact that some of the sources and sinks were large compared to human emissions and that the various sources he found on the internet had somewhat different estimates of the quantities.
Now the fact is that the carbon cycle is conveniently divided into slow and rapid components. Humans are currently putting something like 10^15 grams of carbon into the atmosphere every year. The fast carbon cycle (mostly biological photosynthesis and oxidation) involves one or two orders of magnitude more carbon, but almost all of that is stored only very temporarily. The slow carbon cycle (volcanism and precipitation of carbonates, for example) involves a order or two of magnitude less than humans are putting into the atmosphere. These can store carbon for millions of years. Failure to recognize this cardinal difference means missing the point: Fast carbon cycle processes only store carbon for a short time.