Because he challenged their elitist ways to have slave labor, and were worried this could mean no more fancy homes, no more being able to control people and pontificate moral edicts to everybody else about what they feel civilized people should do, say, behave, etc. Although today, instead of having the people below them being called, "slaves" they now are the undocumented immigrants, and minority low skilled American labor workers, who they believe they are better than, and want to ensure such people cannot elevate themselves in society, so want to increase the low skilled labor pool to force low skilled workers no alternative but to accept dirt cheap wages, so they are stuck living dependent off the democrat law maker's welfare policies, so they can continue to control them in every way, just as their forefather slave owner party predecessors did.
But the most ironic part about all this, is that Democrats are so pathetic that they have to hijack the Republican's party's history, and claim it as their own, because they are apparently still in denial about who they are...
The icing on the cake, is that they apparently also are trying to claim that these democrats, who they claim to now have nothing to do with, are now evidently reaching the age of 170 years, and are now voting republican. If this is true, then they have defied all known human biology and life expectancy estimates as we know. Or are just making pathetic ridiculous claims, hoping somebody will actually fall for their nonsensical garble. I also noticed, they never seem to factor in, that the people who got freed, became republican, which was the biggest reason the south suddenly became full of republicans, since they now could vote, and that's where all the freed slaves were living.
All I can say is, it sure must suck to be a democrat, and have to make such ridiculous arguments to justify your crappy past.