Dr. King's thoughts on the Democratic Party in the early 60s are completely irrelevant to the modern party - it's not even remotely the same voting bloc. The electoral map in the election directly preceding his Letter from a Birmingham Jail looked like this:
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To be fair, I thought you'd look at a better viewpoint than just a map. You're presenting an extreme straw man argument here.
The point is policies.
In 60+ years, in real terms, how much has actually changed for the Black and working class community? I'll answer for you; not too much if 'the great US democracy' worked so well it allowed someone like Pres Orange to occupy the White House.
Surely, for pete's sakes, SURELY that much is obvious?!!
Obama compromised in order not to be seen as 'uppity' and got fuck all for his moral victory. Bailed out rich companies and fuck over the little people leaving them with lectures as a leaving present. So, in steps the Orange Buffoon because people got disillusioned with the process and lives not improving.
You can show me all the maps in the world, but Dr King's message( in which the paragraph chosen is not confined by the hallmark of its time) is as relevant today as it was then. He held a deep dislike of incrementalism and 60 years later, people are being told "try again in 3.5 years"!
Liberals, "well meaning" or not, are the ones who hold progress back and there are fucking LOADS on here.