Prior to the Civil War, the Democratic Party was the party that supported slavery and Democratic congressmen and senators always voted for the expansion of slavery into new states. The Democratic party had been promoting and defending slavery since it's beginning.
For a hundred years before the Republican party was created, the Democratic party was promoting slavery and actively working to prevent blacks from having rights. Also, the Democratic party got many laws passed against white abolitionists, such as it was legal to kill any white person hiding a slave. This was to intimidate and eliminate whites in border states (bordering South and North) who were part of the underground rail road (an organised escape route that helped escaped slaves get to the North).
The Democrats were the party of slave owners.
The Republican party was founded by abolitionists expressly for the purpose of preventing slavery spreading to newly formed states. This was the express purpose stated in their founding charter. This was important, because if abolitionists/Republicans could get new states into USA as free states (no slavery) that would give the abolitionists/Republicans the majority votes they'd need to eventually stop slavery everywhere. Another reason why the Republican party was formed was to provide abolitionists political power to pass laws to protect abolitionists from being murdered by pro-slavery people. i.e. - to prevent them from being murdered by Democrats.
After the Civil War, it was the Republican party at the national level in Senate, Congress, and Presidency in Washington DC that tried very hard to get civil rights for blacks for 100 years after the Civil War ended. This continued right through Eisenhower who supported civil right and school integration and used the Army Airborne Big Red One to enforce school integration and prevent violence against blacks.
The Democratic party tried very hard (and successfully) for 100 years after the Civil War to block civil rights using city, county, and state legislative bodies in the South to pass Jim Crow laws to suppress civil rights.
These are historical facts. Martin Luther King was a Republican, but he had to work with Kennedy (a Democrat) because Kennedy was the one in office. Also, Kennedy's heart was in the right place and he really did care about blacks and civil rights. Kennedy was the first Democrat President to be supportive of civil rights.
So anyone who says that Democrats have a better Civil Rights record is wrong. Study history. The Republicans have a vastly better civil rights record.
And I'm not even a Republican. I'm an independent. I have voted for Democrats and Republicans in the past.
Having said all the above, I will end by saying the Democrats have had a good civil rights record since the 1960s. It started with Kennedy. However, there are still, to this day, many Democrats who belong to the KKK.
In another thread, the Republicans were accused of being affiliated with the KKK. Not so. The Republicans have traditionally been the white opposition to the KKK. This is one reason why King was a Republican. In recent times (since the 1960s) more and more Democrats have been against the KKK. As it stands today, the majority of Democrats are now, today, good hearted people who support civil rights and are against the KKK, but the KKK is still a cancer that exists among a minority of the Democrats. i.e. - the KKK are Democrats as they always were. The good news is that those racist Democrats are now only a small minority of Democrats.
So there are the historical facts of life. No Democrat should throw civil rights stones at Republicans considering the historical facts.
How about working together to improve things?