I'd agree that "in general, you should believe yourself" is a simpler rule than "in general, you should believe yourself, except when you come across someone else who has a different belief". And simplicity is a plus. There are good reasons to prefer simple rules.

The question is whether this simplicity outweighs the theoretical arguments that greater accuracy can be attained by using the more complex rule. Perhaps someone who sufficiently values simplicity can reasonably argue for adopting the first rule.

ETA: Maybe I am wrong about the first rule: it should be "in general, you should believe yourself, except when you come across evidence that you are wrong". And then the question is, how strong evidence is it to meet someone who came up with a different view. But this brings us back to the symmetry argument that that is actually a lot stronger evidence than most people imagine.