Lincoln was definitely racist, but relative to his time he was a raging liberal. He believed strongly in abolition (again for the third time this was the fundamental issue the Republican party was built on) but he struggled to personally view black people as equal.
The Republicans were an abolitionist party. They ran Lincoln, who won, and when that happened the slave states started seceding, specifically citing slavery as the reason for their split. I can post the declarations of independence of some confederate states if you nazis need some primary sources. I'm always happy to educate.