Argument from ignorance. They were in the same league from the point of view of their victims.

But if you believed that doing so was somehow right (again, the "greatest good" nonsense or something), then it's OK?

I never said that. From available evidence, not one of the people you mentioned did their atrocities for the ``greatest good'', and it would not matter if that was the case, because the willingness to commit atrocities is the monstrous thing.