> It is considered acceptable - by certain people with a political ax to
 > grind. That does not change the fact that it is grammatically incorrect.

That was decades ago; get over it.  In language, theory follows
practice.  Singular "they" is a done deal.

I'm about ready to admit defeat in my campaign to get people to
pronounce the metric prefix for a billion, "giga", correctly:
It's a soft g, as in "giant".  I think the computer industry
originally botched this, but their pronunciation took over
because they were the first to provide common folk a billion of
anything worth counting.

--
--Bryan