"There were surly no mass hangings of secessionists"
But there were mass hangings, lynchings would be more accurate, of blacks during draft riots in Union territory.
Yes there were. And they were all hung by pro Confederate mobs incited by Copperhead NYC Mayor, Fernando Wood. Union troops restored order and protected the blacks of New York City. The troops should have hung Wood.
Those hangings were by anti-war Democrats and gangs only in NY city.