Very interesting lack of responsiveness to your question.
If you are correct that an orthodox Muslim cannot condemn a fellow Muslim who is engaged in conflict with non-Muslims, I find it difficult to understand why.
Especially when the Muslim's conduct is obviously in direct conflict with Muslim law, as in the case we've been discussing.
Islam is a religion of battle and conquest. One thing a military commander CANNOT allow (and Mohammed WAS a military commander) is factional fighting among his forces. Even worse would be a faction going over to the enemy (infidel) side. Not taking the side of the infidel aginst a Muslim is one of the strongest taboos of Islamic culture (as strela has demonstrated).