I won't fault Ann for channeling her inner Ron Paul; I have a bit of that myself. And past is unfailingly prologue, then Trump messed up, big league. However, there is another way to look at the thing.
Trump responded to the use of a WMD. And his response was swift. He (and Mattis) claim the evidence is conclusive and Turkey said the victims they received had been exposed to sarin. (And it does not matter if Assad dropped a chem bomb or blew up chemicals stored on the ground. He is the responsible agent for their being in country)
Consider what we would be discussing had if we had sent a stern letter. I guarantee we would be hearing: "Is Trump really Obama 2.0?"
I do continue to be disappointed in Trump's comm shop - I thought Spicer was going bad even before his Hitler brain fart. His mouth outruns his brain when he tries to get into tit for tat with the media. He needs to go. What is needed, in this matter of response to WMD, is a clear message that paints the picture of a future with them in the hands of ISIS. Consider Madison Square Garden or the Tokyo subway.
Accusing Trump of a flip-flop is shooting fish in a barrel easy. A competent comm operation would be all over that with the message that the President has become THE responsible agent and fulfilled his responsibility in making it clear that a red line is really and truly red.