I find it slightly ironic to assert the subjectivity of literary criticism as part of a defence of JRRT, given his own views about the relationship between knowledge, truth, language and (what he called) "sub-creation".That wasn’t the context of his quote.
And before we go further with his view of peoples of the east in terms of Mordor being of the east and such, again, it’s important to remember that’s a subjective interpretation not a literal statement from the author that is what it is.
If we are to engage in literary theory, critiquing work, it is imperative one must remember that it is fully subjective and we bring our own experiences and baggage within our reading and interpretation of it. As Tolkein didn’t explicitly label Mordor = culture x, it has to be subjective. It can’t be stated as an objective smoking gun.
I also don't think the notion of "smoking gun" is relevant here. JRRT is not on trial.
But I think it would be absurd to assert that his location of heroic peoples in the North and West of his imagined world, with the evil coming from the East and South, is coincidence or is arbitrary.
Or, as the propagandists of the time put it, "the Hun".And as an army of soldiers unrelenting bent on the destruction on the west, to me, I’d interpret that more of his visions of the German war machine advancing west wards from his ww1 days.