[ikanreed]

It's a heuristic for understanding why you don't need to take some people seriously with your limited time available to approach new concepts.

Credentialism should never be a fundamental basis for refuting new theories, but it might be a reason to not pay attention to them.

[mcherm]

I would say a reason to limit the attention paid to it. If some crank came to me with a perpetual motion machine I might take 2 minutes to ask them, "So how does this account for the conservation of energy?" If their first response is "Energy conservation doesn't apply at the QUANTUM level." then I can quickly move on and ignore them. If their first response is "I think it is extracting energy from the Earth's rotation through interaction with it's magnetic field." then it may be worth me investing another 5 minutes to see what the next level of reasoning says.