Especially the democrats who were the Slavery Party
1. The Republican Party was founded explicitly to prevent the expansion of slavery to new territories and implicitly to abolish slavery everywhere.
2. The Democrat Party and the KKK ended Reconstruction and implemented Jim Crow laws to oppress free blacks for 90 years.
3. The 1957 and 1960 Civil Rights Acts proposed by Republicans were stopped by Democrats; and
4. the 1964 Civil Rights Act was opposed by nearly half of the Democrat senators, while 80% of Republican senators voted for it.
Ordinarily, I would oppose someone apologizing for something caused by others, but in this case, if it serves to highlight the complicity and duplicity of Democrats, I say: have at it!