Your confusing Democratic and Progressive. The two have only recently become conflated. Republicans were progressive for a long time and Democrats had many conservative trends. It wasn't until the Civil Rights Act that rascists seemed to all become Republican. There are records of many Democrats flipping parties to opppose the Civil Rights Act.
Integration and desegregation are progressive and have been since America was founded. If it is ever well founded for generations, there could be a "progressive" movement to segregate, but since the status quo is segregation, the progressive policy is integration and desegregation. The rioters opposing this were conservative, they were seeking to maintain the status quo, the same as the South in the Civil War. They lost at the Ballot box and went to violence and riots. It's not a progressive method, it's a human method.
It's also possible for people to mix progressive and conservative policies. Even Obama was conservative on many issues.
Your "statement that there was no clear link between the plight of blacks today and 19th century slavery; in fact, blacks today tend to be poorer largely as a consequence of segregation, eugenics, and the destruction of the black family" Is partially true, those policies of segregation, eugenics, and black family destruction are well documented and resulted from a mix of conservative and progressive policies. Many of the progressive policies were "modified" by vile rascists to facilitate this, similar to how the Republicans supported black in government jobs until Woodrow Wilson purged them.
Your also missing the clear policies enacted by local, state, and federal policy makers that prevented blacks from living in certain areas or taking certain jobs. Claiming none of this is related to slavery, is a falsehood.
There have never been any reparations for slavery. Slavery prevented generations of African's from handing down wealth and creating strong family bonds. Slavery and subsequent laws prevented black from getting educated, created rifts between house and field slaves. Slavery allowed the rape of black women and the created the inferiority complex of poor whites. All of these issues and more are deeply affecting our culture today. They've influenced how blacks and whites interact, contributed to racism, and allowed "progressives" to advocate the scientific inferiority of blacks.
Now that I see where you are misled, I apologize for my earlier frustration. It's easy for someone only familiar with today political climate to assume Democrats are Progressive and Republicans are Conservative in history books.