As you seem to have guessed, many scientists do in fact think these past climates rule out the possibility that the earth could be as insensitive to greenhouse gases as Richard Lindzen and other skeptics believe. But, even if you accept that, it doesn’t necessarily tell us much about the time scale on which the earth adjusts to higher carbon dioxide. Are we going to have a sea-level crisis in 50 years, or 3,000 years? That’s a pretty big difference for somebody trying to create government policy.
[comment] Does [Gillis] even have a degree in any scientific discipline? I can't find a bio for him online.
Lying and bamboozling the public with his own agenda for so long does not make him an expert on anything but being a liar and con man.