The biggest threat to the denial of any scientific fact is evidence showing that there is a scientific consensus. Scientists are sceptical and questioning by their very nature. They love to poke and prod everything to see if it withstands scrutiny.
When scientists agree this is a sign that some serious prodding has ensued and that the evidence withstood it. That’s why studies like Oreskes 2004, Doran 2009, Anderegg 2010, and Cook 2013 showing that scientists agree the planet is warming and that we’re causing it are such a threat to science denial. Which then make them a prime target for attacks, I have more than enough articles on this website chronicling the attacks on just the Cook 2013 paper.