The Left also ignores the firebombings of Tokyo, which killed over 100,000. And I believe the reason for that is that if they admit that the Tokyo bombings were war crimes, they'd have to then admit the same about Dresden and Hamburg. ...which of course were during their hero FDR's time. And criticism of FDR is verboten under any circumstances.
(For the record, I personally don't think any of the above acts of war were war crimes).