" It is not enough, when proposing a theory of everything, to demonstrate that someone else
is proceeding on fallacious assumptions. "

It is enough if the only point you are trying to make is that someone else doesn't know what they are talking about.

" One must guard against [fallacious assumptions] one's self "

That is impossible. All assumptions are fallacious. An assumption is a claim to be in possession of knowledge one clearly doesn't possess. Call it by any other name, it remains a fallacy.

The only knowledge one can possibly have is the knowledge one already has. Beyond that, there's only self-delusion.