Who were the right terrorists?
The Americans want Russia to bomb Assad instead bombing the Islamists.
The United States doesn't care much about the situation in Syria, but the country is extremely significant for some of the American allies such as Saudi Arabia, Qatar, Turkey, and Israel. Israel want to remove the Hizbollah, which is supported by Assad. Saudi, Qatar, and Turkey want to construct a gas and oil pipeline through Syria, after toppling Assad.
So they have "tactically" supported some "good" terrorists, such as Jabhat al Nusra and the ISIS. The Arabs have channeled billions of USD worth of weapons and other supplies to them. Now all of that is going up in flames, as a result of the Russian airstrikes.