How is it revisionist, when people that he rescued, or their descendents are still living in the US? This information comes from a Rabbi, after all.
How many people did your ancestors rescue from slavery in the USA to move them to Canada via the underground railroad?
It makes as much sense to say that all Americans supported slavery pre-Civil War, as to say that all Germans in the late 1930s were Nazis. Long after the Civil war was over, there was still the apartheid of segregation until the civil rights movement struggles ended them.
Anybody want to get into the genocide against the Native peoples of the Americas during the westward expansion of the USA?
Don't so easily condemn others for the crimes that we did here also.