Straw man...and yet there is truth in what you say. Northerners were oppressors of blacks. That truth might be hard for you to swallow, but there it is.
"[R]ace prejudice seems stronger in those states that have abolished slavery than in those where it still exists, and nowhere is it more intolerant than in those states where slavery was never known." --Alexis De Tocqueville, Democracy in America"
And yet runaway slaves made their way north. If their lot was so oppressed there, why did they continually attempt to go there? Could it be that it was comparatively less oppressive than the south?
"[R]ace prejudice seems stronger in those states that have abolished slavery than in those where it still exists, and nowhere is it more intolerant than in those states where slavery was never known." --Alexis De Tocqueville, Democracy in America"
I suppose one is inclined to be tolerant of their property.