This is a very tentative stab at elaborating some thoughts that have been rattling around in my mind for a while. The occasion for the attempt is Charles Blow's column in the Times, in which he writes, "Everything that springs from [Trump], every person who supports him, every staffer who shields him, every legislator who defends him, is an offense. Every partisan who uses him — against all he or she has ever claimed to champion — to advance a political agenda and, in so doing, places party over country, is an offense."
One of the things that has sprung from Trump is Neil Gorsuch, whose appointment he claims as one of his (few) achievements so far. Many on the right who purport to oppose Trump-ism generally apparently approve of Gorsuch's appointment. I've thought for a while (and noted it on Facebook) that this struck me as resembling the nominal opponents of Mussolini who are said to said, "Well at least he made the trains run on time." (Apparently he didn't, but that's beside the point.) The phrase is used, I think, to criticize people who, though seeming to distance themselves from the parts of Mussolini's program of which they disapproved, were actually complicit in his entire program.
In Masterpiece Cakes and similar cases, religious (and other) conservatives seem to take the position that -- at least within extremely broad limits -- a person's claim that taking some action would make him her her complicit in a moral evil, has to be taken as conclusive for some constitutional or statutory purposes. (The constitutional part of that involves "hybrid" claims under Smith; the statutory part involves RFRA-type statutes that do more than re-state pre-Smith law.) The complicity claim can be overridden for compelling reasons, but not otherwise. This is what I think of as an internal complicity claim.
The Mussolini "argument" involves what I think of as an external complicity claim. The person being criticized expressly does not think of himself or herself as being complicit with Trump generally, but (not to put a fine point on it) I do. I'm pretty sure that there have to be some limits to external complicity arguments, but I'm not sure what they would be. One candidate would be something like this: Gorsuch's appointment is a happy by-product of an otherwise dreadful event. But, at least as far as I've been able to think this through, the appointment isn't an accidental by-product; it flows from the powers conferred on Trump by his election. So, to get the purported by-product you have to get the whole package.
It's also pretty clear to me that external complicity could be offset by equivalent actions rejecting the loathsome parts of the Trump program. And, in the present context, maybe the people I have in mind are doing no more than expressing approval of the Gorsuch nomination and are elsewhere offsetting that by expressing disapproval of other parts of Trump-ism. At this point in my thinking, that leads me to think that the problem of external complicity imposes an obligation to take offsetting actions -- and, in particular, overrides the usually correct view that bloggers and Facebook posters have no duty to address matters they choose not to address. That is, it is usually true that a fully adequate response to the question, "You've posted on Masterpiece Cakes; why haven't you posted on [fill in the blank]?," is "Because I didn't want to." My current view is that someone who posts approvingly about the Gorsuch nomination, including an approving post about a Gorsuch opinion (the program wants to autocorrect that to "Grouch"!), incurs a duty to offset that post with something critical of some (other) aspect of Trump-ism.
But all that might be entirely wrong. Maybe the only coherent concept of external complicity is that one can be complicit only in the substantively loathsome aspects of Trump-ism, of which the Grouch appointment is not (by assumption) one. Then I wonder about the status of arguments laying out the best legal case for the Trump travel ban, motivated by anything other than the Mill-ian desire to ensure that the ban's opponents will be in a position to counter those arguments.