Should connotes that the political & military leadership made a mistake and they should've known that bombing Auschwitz was a better choice (than bombing Schweinfurt, e.g.). I'd contend that, even knowing what we know today, that may not be the case.
Moreover, expressing remorse doesn't necessarily require one to question the decisions that FDR/Ike had to make in the context of their knowledge in 1944.
It's not a big deal. But it is unfortunate -- in the same way that people criticize Jefferson for being a slaveholder is unfortunate.
You and I just disagree. You can certainly criticize Jefferson for holding slaves, yet fully respect him for all the good that he did.
He wasn’t perfect.