The first point is Rebel as in:-
a person who refuses allegiance to, resists, or rises in arms against the government or ruler of his or her country
a person who resists any authority, control or tradition
Where the rebels were of a type we disapproved of (in Iraq, after the Anglo-American invasion), they were ‘insurgents’. Had they been approved of, they would have been the ‘resistance’.
Likewise, in Syria, ‘our side’ must not be called ‘rebels’ or ‘revolutionaries’. They are called ‘activists’, a word so meaningless that it demands analysis.
Of course support can be given or taken to one side or the other just on the terms used to describe them. This is bizarre...