Dear Jack,

the 'merchants of doubt' describes a very specific group of online grifters. Namely those who spread disinformation that runs contra to the currently held scientific belief, all without supportive evidence. They purposefully discredit and 'sow doubt' about what facts are established and 'likely' true so they could spread a malicious counternarrative that puts them and their pet theories in the center.

If you want some recent examples, think about Robert Malone, Bret & Eric Weinstein, McCulloch, and a host of others about vaccine safety/ivermectin. On the 'lab leak' theory, look at people like Matt Ridley and Alina Chan. I mean, the list is pretty endless to be honest, a good proxy might be a set of people who are 'famous' or have a large following online while being scorned by scientific experts.