That little nugget of info wasn't known until after the war (or if it was known, it wasn't a concern). Using the holocaust as justification for allied actions in WWII is seriously misrepresenting the historical record, you know this. In fact, this is one of the things that really gets to me when people say "but Hitler was so much more evil". Yes, perhaps he was, but people did not know this at the time. So much of the justification for the allies and the demonisation of the axis is post hoc.