The Obama Administration rightly stayed out of Syria through six painful, grisly years of civil war there. Yes, the fighting has cost hundreds of thousands of lives and displaced millions. Yes, the uncontrolled migration of Syrians to Europe caused deep problems there. Yes, the Kurds are sympathetic. Yes, Barack Obama made a fool of himself when he declared the Assad regime's use of chemical weapons a "red line" and proceeded not to enforce it.
Despite all this, it was right not to intervene because Iranian- and Russian-backed Shi'ite pro-government jihadis are best kept busy fighting Saudi-, Qatar-, and Turkish-backed anti-government Sunni jihadis; because Kurds, however appealing, are not contenders for control of the whole of Syria; and because Americans have no stomach for another Middle Eastern war.
The direct American involvement that a few hours ago with nearly 60 cruise missiles in an hour attacking Shayrat Air Base implies siding with one side against the other, even though both of them are hideously repugnant. (While the regime has done the great preponderance of the killing, estimated at 94 percent, that's due only to its greater destructive power, not the humanitarianism of ISIS and its other enemies.)
I see this military action as an error. Nothing in the U.S. Constitution requires that American forces fight in every war around the world; this one should be sat out, letting enemies of the United States fight each other to exhaustion.
The immense resources of the United States should be dedicated, rather, to two goals: reduce human suffering with blankets and soup and prevent the stronger side (now the regime) from winning through the provision of intelligence and arms to the weaker side (the Sunni rebels).
Trump should immediately cease all direct attacks on the Syrian regime and instead help its enemies to fight it more effectively. (April 6, 2017)
Feb. 8, 2018 update: And if the above were not reason enough to stay out, Secretary of Defense James Mattis has now acknowledged that the U.S. government has "no evidence" that the Assad regime deployed Sarin gas against its subject population in April 2017.