I think that the "liberals are the real racists" / "Democrats were the party of slavery" rhetoric can be summed up in this image:
"Racism" was invented by Jєωιѕн Marxists
specifically to target and vilify (and, increasingly, to de-kulakize) white people. The proper response to charges of "racism" is to call this invented, non-existent moral fiction out for what it is, not to try to turn it around against its creators, and thereby legitimize their own concept.
This should be self-evident. Would "liberals are the real homophobes" make an iota of rhetorical sense? I think we're presently not much more than five years away from that becoming a Republican party talking point.