I'll also say that this is not unique to him, it's how conspiracy minded people operate.

You'll see exactly this playbook playout with flat earthers. "We can't know the earth is round because it's not been tested." or "It's actually industry captured" or "The US government prevents people from doing real tests to see if the earth is flat".

You see, if you asked them "what would it take for you to abandon this theory" their honest answer is "nothing" because any counter evidence to the theory will just get wrapped up in more conspiracy.

What would it take for me to abandon my belief in evolution? Evidence that explains why things appear to evolve and shows what actually happens instead.

What will make me abandon my support of vaccination? Evidence that shows vaccines are more dangerous than the diseases they protect against.

I have avoided so many pointless arguments (or "debates") by leading with this question! I ask, "is there something I could say that would make you change your mind?" If the answer is no—if they can't tell me what will move them off their position—then I can say, "well let's not waste our time here, yeah?" and change the subject.

It's not perfect. But with otherwise-reasonable people, it's a nifty trick.