Trump's comment was correct, more or less. Either Clinton doesn't know who the rebels are or is so consumed by enmity for Putin and Assad that she doesn't care.
Trump was also right that rebels often turn out to be worse than the strongmen they topple. In real life, Muammar Gaddafi was a grotesque goon. But compared to some of the Salafist head choppers who have filled the resulting power void in Libya, he seems more like Desmond Tutu in retrospect.
Much the same can be said for Assad. Arguably, he is little more than a Syrian Michael Corleone. But after somehow managing to survive five years of a U.S.-Turkish-Saudi onslaught -- and in comparison to the barbarous Al Qaeda and ISIS fanatics operating in Syria -- he now seems like Nelson Mandela.
In any event, Hillary Clinton has made it crystal clear. Anyone who votes for her is voting for greatly expanded warfare in the Middle East and probably military confrontation with Russia elsewhere as well. As bad as things are in Syria, in a few months they could get a lot worse. Don't say you weren't warned.
[For more on this topic, see Consortiumnews.com's "Yes, Hillary Clinton Is a Neocon."]