> While skeptical, he did not have much skepticism against mainstream theories.

That's tautological. The definition of a "mainstream theory" is one that is widely believed. And while, sure, sometimes scientific paradigms are wrong (c.f. Kuhn), that's rare. Demanding someone be "skeptical" of theories that end up wrong is isomorphic to demanding that they be a preternatural genius in all things able to see through mistakes that all the world's experts cannot. That doesn't work.

(It's 100% not enough just to apply a null hypothesis argument, btw!)

Really that's all of a piece with his argument. It's not a recipe for detecting truth (he didn't have one, and neither do you[1]). It's a recipe for detecting when arguments are unsupported by scientific consensus. That's not the same thing, but it's closer than other stuff like "trust".

(And it's 100% better th an applying a null-hypothesis argument, to be clear.)

[1] Well, we do, but it's called "the scientific method" and it's really, really hard. Not something to deploy in an internet argument.