If it's true that "black" is similarly pejorative to the "N" word, which the reaction seems designed to suggest, then it's easy enough not to use that word. Otherwise, perhaps the accusation of bigotry is a convenient fig leaf to disguise "protesting too much" about your scathing depictions of their party. In which case you can let it go now. ;-)
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
