It's true. The problem is that they will not accept that their fantasies are just that. If somebody shows them Einstein saying space is inhomogeneous or the speed of light varies with position, the crackpot will utterly reject it, and comfort themselves by calling the other guy a crackpot. Even though what Einstein said is there in black and white and a matter of public record, with professional endorsement. It is truly bizarre.
The funny thing is, I don't believe in GR
just because Einstein said it. I believe in GR because it's been carefully tested, by people (a) checking its equations for internal consistency and (b) devising experimental measurements and comparing them to GR calculations.
The thing I strongly believe to be true is that
actual GR calculations, using Einstein's GR equations, are internally consistent and have passed extraordinarily-stringent experimental tests. The equations, in the form used to make the predictions, are widely taught, researched, explained in standard textbooks, and the meaning thus conveyed is uncontroversial. This is what I mean when I say "I believe GR is true" or "I know/understand GR". I know the same version everyone else knows,
the version that's passed experimental tests.
I furthermore believe that Einstein was talking about
the same GR that I believe in, and that his words have a reasonably clear meaning to people other than yourself, you being a hostile witness who's actively mining for things to misunderstanding.
However, my belief in the latter is
much weaker than my belief in the former.
The
standard version of GR, the equationy version, the Misner Thorne and Wheeler version, has been tested, and I'm happy to have learned it and to understand it well and to be confident in its reliability (within the domains in which such confidence is warranted), and everyone who claims to know GR will say the same thing.
If it were true that Einstein's popular writings describe
something else---some equationless theory that's
not the one MTW picked up on---well, this "something else" theory would be untested, undeveloped, cannot be called "General Relativity", and would not inherit the intellectual heritage of the known/tested/taught version of GR. (I reiterate that you have not identified a "something else" in Einstein's writings, only familiar things that you personally misunderstood.)
Can you take
your interpretation of Einstein's words and make
your prediction for, say, the inspiral of the Hulse-Taylor binary pulsar? Go ahead.