Yes the Republican party was/is opposed to slavery, Jim Crow and favors civil rights. That said, the north fought the civil war to maintain the union. Lincoln learned that northerners would not fight and die for the black man. It was the Union army, not the Emancipation army, that defeated the south.
You say that the Republican party supported the working man, and various liberals say the Republican party is the party of the rich. This kind of class warfare talk is not conservative, it is more