An utterly idiotic mistake that should be punished, but a mistake nonetheless. Do you care about the fact that the Kiev junta is indiscriminately bombing its own cities? I don't think you do.
As a communist you should understand how a civil war works. You don't get to raise arms against the established state and then whine when they respond with force.
The benefit of a rebel fighter is that if you take away his gun after he dies he becomes another "civilian killed by his own government". It's utter dishonesty in the same strain as employed by Syrian rebels.
But they are politically aligned against the West, so I understand you are obligated to support them regardless.