Back in the day, the Dem's used to be the the "Party of sticking up for the little guy" and the Repubs were the party of the big guy (ie, businessmen).
Then in the 50's and 60's, the Dem leadership started to say "wait, minorities in this country are getting an even worse shake than the average white person and we need to stick up for them, too!".
Well, there goes all your southern blue collar workers. By the end of the 60's and throughout the 70's you saw a mass exodus of southern blue collar voters from the Dems to the Repubs who were now saying "Hey, come be with the job creators (white people!) and screw those "takers" (minorities).
Even though the Repubs went on being the party of big business, systematically screwing over the workers (via NAFTA, support of offshoring, undermining workers unions, etc) now you see the results, the middle of this country is much worse off because of these "business friendly" policies.
Here's the thing. I'm from the South. Those people are racist as hell. That's not going to change. The more you challenge them on it, the more they just double down. If the Dems want to win again, they'll stop talking about race and start talking about economics and go back to being the party of the little guy.
And in fact, this is my theory why Trump got elected. Even though he's not really a classic Republican. It's really because he's the first Republican in a generation to say "Wow, our trade policies (like NAFTA) are terrible and it really screwed you people in the middle of the country!". And THAT's the reason Trump carried those middle swing states. He's finally saying that the policies of the past 40 years have screwed the blue collar workers and they are like "Hell yeah".