Maybe CWII will not be what we expect. Instead of Left versus Right, how about Left versus Left, since they would be violently preoccupied with ideological purity within their own ranks? Let them kill each other. Just stand ready if it spills over. Otherwise, get the popcorn.
You make a good point. Juat as shia hate sunni, and stalin had trotsky murdered, it is quite likely that one set of lefties will declare war on a different set — heresy is a major crime for the true believers.