If indeed ancient farmers (that were like 1/100 our population) already had "profoundly changed Earth's climate", so much for the "human activity couldn't be the reason for climate change today" argument...
Furthermore, "the reason" can usually be whatever you want it to be if you go far enough back in the chain of causations. My hands were wet this morning when I dropped the jelly jar. But that wasn't my fault, it was the water company's fault for supplying the wetness on my hands. Or perhaps it was the Roman's fault for kickstarting the whole thing with aqueducts. But that's really just mankind's fault for existing, so human activity is at fault for my loose grip on the jelly jar today.
Overall, I found this article interesting, and frankly: Go mankind! We averted an ice age and certain death/destruction with farming. If we want to talk about problematic climate change, look at how living on top of a mile of ice works out for our species.
One could very well imagine (and some of us actually know) people that legitimately believe that the climate change we're through is not man made -- they say it cause they believe it, they don't try to knowingly deceive anyone.
It's another thing to say something because you do not trust scientists (including scientific consensus) because e.g. you believe that they extrapolate from incomplete data and not enough understanding, or to prefer this or that fringe researcher to the majority opinion, and another to be in bad faith.
Rather, beliefs appear to be more about identity, virtue signaling, and tribal acceptance.
If true, reason is impotent. To change belief systems, one must use psychology, rhetoric, propaganda, evangelism.
The lesswrong.com crowd is calling this "belief as attire". I don't know what to call "Popperian beliefs" (true until proven false) vs "aspirational beliefs" (make our own reality).
My greatest fear is that my self-image of being a Popperian is actually just aspirational.