There is no such thing as "settled science." Science is a constantly evolving body of knowledge that by its very nature should demand an ever higher burden of proof.
They called the lipid hypothesis settled science, there was a time when it was a "scientific fact" that the smallest particles in the universe were atoms. It was very recently that it was "settled science" that no particle of matter could be in two places at the same time. All of these "facts" have been tested and shown to be either over simplifications or just wrong.
Any one that calls something "settled science" is trying to shut down a conversation. The next step is to label those that disagree and then to isolate them.
I don't if man made global warming actually occurs. I am no scientist, but i do know that using intellectual and economic fascism to silence opposition is not science.
Yes, people are allowed to have any and all opinions. Just like others are allowed to ignore fringe elements in order to be productive.
The simple fact is ignoring this issue will have exceptionally grave consequences if man-made global warming is true. These guys want to wait for "proof" which will only exist after the climate and ecosystem as we know it has been destroyed.
I can ask a 100th time what the fallacy with the basic cause behind global warming is and the question will be removed from the quote and ignored for the 100th time.