The whole US response to the Syrian civil war is/has been a dog's breakfast from start to finish (or at least to the current moment, not like it's quite over). The reality is you're basically choosing between a strongman who is doing all sorts of naughty things you don't like, or a bunch of religious loons who will work day and night to make sure said strongman looks like Winnie the Pooh. Just exactly how the State Department KEEPS deciding that if we support religious fanatics they will suddenly embrace Western values is 100% beyond me. We're naught for how many now?
Edit: AFAICT, there aren't a lot of actual Ukranian Nazis, it's not an apples-to-apples comparison. Certainly, they exist, but I would paint our intervention in Ukraine as kind of the opposite of our various abject failures in the Middle East. Like, Ukrainians are increasingly well-disposed towards the West, and increasingly interested in joining the, for want of a better term, modern world. Perhaps both because they have both a more similar world-view (including religion, obviously) to the West and (I think more importantly) they have real, long-term, and relatively recent experience with the alternative being presented by the East.