Here's a question: what do you mean by ignorance? Let me rephrase it: suppose one is a…say…basic particles physicist. Poor guy (don't jump, all applies equally to the ladies) doesn't possess a clue about climate sciences. This guy hears about all the GW debate and gets curious. He reads a book or two, googles around some, watches 2-3 TV shows, watches this Nobel laureate - Oskar winner 's film and concludes that GW might be real but, to his liking, there is not enough evidence to support a notion that the anthropogenic component has significant enough roll in GW.
It depends.
Is he denying the role of GHG? The physics is well established.
Is he denying the temperature record? The data and the methods are public and have been scrutinized.
Is he denying the proxy reconstructions? Multiple reconstructions have been made and are in agreement?
Is he denying the role of anthropogenic CO2? Isotope analysis puts it as a major contribution for the CO2 accumulation.
Where is he get this "lack of evidence"?
And if he has scientific training, why isn't he treating it as such? TV shows? Al Gore? A poor scientist this guy is turning out to be.
Is he bringing anything to the debate? A new understanding of the physics of GHG? A new way to compute the global data? Improvement of the models?
Remember, he does not have MSc. in climate, however he can recognize scientific reasoning and evidence should such be presented.
If he can, he should know to defer to the scientists that are working on this for years, or at least ask politely to be referred to the appropriate literature. After all, how would he feel if a paleontologist decided to second guess his work because he saw a couple of PBS NOVA's?
Would you let him "have a say" on the AGW/GW debate or you would call him names (ignorant, immoral…)? Attention: I am not asking whether you agree with this guy or not.
No, he shouldn't have a say in the virtually nonexistent AGW/GW scientific debate. If he wants to, he should go the normal way in science. Research, publish, convince. He also shouldn't have a say in the very existent, highly political debate regarding AGW/GW. Politicians should be advised by the leading experts in the field, not by amateurs.
Tell me, would your particle physicist also want to join the debates on fisheries? Biodiversity? Ocean acidification?
At what point does your physicist think to himself "maybe I'm out of my depth and making a huge ass of myself"?
That hubris is immoral, as are it's consequences. That's why you got the infamous lists of "scientists" against AGW: arrogant idiots wanting to make a stand on a subject they didn't grasp. I'm not counting here the people whose names were added fraudulently to those lists, of course.