This is the same silly game Prager plays in his book - pretending that since the Republican party was the liberal party when Lincoln was President, they're still the liberal party today. In fact, it wasn't "the Left" defending the right to own slaves. Then, as now, that was conservatives doing what conservatives do - conserving the status quo. It was "the Left" which fought to abolish slavery, and yes, at the time that meant the Republicans. In fact, up until the 1960s, when the reactionary descendents of slaveholders, the "Dixiecrats," decided the Democratic party was too liberal for them and deserted it (some, like Strom Thurmond became Republicans), it DID attract most of the racists. Most racists are now Republicans or Tea Party.