People already do that, and yet rationalists see no reason to 'shut up shop' as a result

People try to do that, but rationalists don't have to regard it as legitimate, and can object. However, if a notion of truth is adopted that is pluralistic and has no constraint on its pluralism --Anythng Goes -- rationalists could no longer object to,eg. Astrological Truth.

'True' is just a word.

Rationality is about systematic optimization for our goals, not about defending our favorite words from the rabble.

So you say. Most rationalists are engaged in some sort of wider debate.

sometimes it's worthwhile to participate in the gerrymandering

Even if it is intellectually dishonest to do so?

First, it might be gerrymandered for purely social reasons. Second, it might be gerrymandered because it's a very complicated property of high-level representational systems.

I think you may have confused truth with statesof-mind-having-content-about-truth. Electrons are simple, thoughts about them aren't.

One should not expect mental states in general to be simply and nondisjunctively definable in a strictly physical language. Yet if we learned that 'pain' were a highly disjunctive property rather than a natural kind, this would give us no reason to stop deeming pain unpleasant.

Somethings not being a natural kind, is not justification for arbitrarily changing its definition. I don't get to redefine the taste of chocolate as a kind of pain.