See also: the wikipedia article on cranks. If you are still unsure, try the crackpot index . My fave: you receive 20 points for naming your crackpot theory after yourself. Also: 10 points for arguing that a current well-established theory is "only a theory", as if this were somehow a point against it. Also, significantly: 50 points for claiming you have a revolutionary theory but giving no concrete testable predictions.
With respect to climate problem, my problem is with naysayers who criticize the “theory” of climate change without making a plausible prediction about the future. From a rhetorical standpoint, it is nearly impossible to respond to the naysayers who say, “it’s only a theory.” A future post will be dedicated to how to respond effectively to that.