Surveying the range of opinion that has been expressed on Syria, the positions of various ideological factions seem to be breaking down along these lines.
The entire spectrum of the “mainstream media” seems to be cheerleading for the attacks on Syria. Of course, the spectrum from MSNBC to FOX is not that wide of a spectrum. A couple of happy exceptions among the FOX crowd have been Tucker Carlson and Tomi Lahren.
On the question of Syria, I’ve noticed that centrist-liberals (the Rachel Maddow fans that Caleb Maupin, and I, bemoan) are generally pro-war, while the actual left (generally) is not (from what I can tell so far). However, I’ve noticed that a lot of the “antifascist” types are more concerned about “far right entryism” and “red/brown alliances” than actual imperialism. A lot of other leftists tend to treat imperialism as just another laundry list issue along among the spectrum of conventional “social justice” interests (which I think is a mistake). There are still others that may be against the war in theory, but are more worried about “microagressions.”
I think the Left has had two major problems when it comes to this question. First, co-optation by the neoliberal center (Democrats) and subordinating issues of these kinds to idpol on the far left. Obviously, there are exceptions (Counterpunch, Black Agenda Report, Jill Stein, Dissident Voice, Jimmie Dore, Abby Martin, etc). but those have been the exceptions rather than the rule.
Of course, the Rothbardian libertarians are good on foreign policy generally, and consistently oppose all US imperialist wars. Libertarians, with some exceptions, are generally pretty good on foreign policy, although like the Left they often treat foreign policy as “just another issue” along with “school choice” and “tax cuts.” The paleoconservatives, the “far right,” and the Alt-Right have likewise stepped up to the plate on Syria, largely on isolationist, pro-Assad, anti-Israel or Eurasianist grounds. The “far right” in all of its configurations has emerged as the most consistently anti-intervention milieu in the last 15 years or so, although these sectors also treat foreign policy as “just another issue,” and secondary to opposition to immigration, and other standard “far right” issues.