Spicer makes a sloppy but relevant comment about Assad, pointing out that even Hitler didn't indiscriminately use battlefield chemical weapons on the general population.
He is compelled to apologize because it's not acceptable*, to the perpetually outraged, to refer to "Holocaust Stuff" either flippantly or hyperbolically.
And yet millions of those same perpetually outraged assholes have been calling Trump "LITERALLY Hitler" for over six months, with zero basis for their flippant and hyperbolic accusations, and have yet to apologize for anything.
The hypocrisy is palpable.
*only for non-democrats, apparently