I'm not well versed enough on this subject to lead a substantive discussion but he seems to overstate his position without verifiable sources, for example, "The vast majority of refugees now entering Europe are fleeing Assad's murder machine, not ISIS or al-Qaida.", and, "[Assad] has been responsible for 95 percent of all 111,000 civilian deaths since 2011." Granted, he may know exactly what he's talking about as his experience and background seems to qualify him. But I'll take these assertions in particular with a grain of salt, the situation is very complex and fluid.
Generally I agree with the premise, there is no cut and dry solution to Syria's ongoing instability and all political actors involved can be pretty much classified as "undesirables". His solution seems to equate to "anything but what Russia's doing" and therefore "anything but Assad", without actually offering an alternative solution. He gets close to advocating politicizing the "organized" resistance through suggestion but refrains from actually stating a solution based this information.
I hate reading critical policy pieces like this that offer no alternative. It's wholly unproductive. He gets close to advocating some substantive change or solution but the substance was perhaps edited out for lack of wanting to commit to his position?