The police powers in Egypt, for the most part, did not attack the protestors, showing at least some respect for the rule of law. Hence, to remove Morsi now would be to demonstrate that raw force supersedes law. Should a new Salafist regime ever take the reins again, they will make sure that can't happen again. It is to inculcate the rule of force.
Although they do exist, there are few historical examples of militarist regimes stepping aside for plurality (Franco and Allende come to mind(, but they are the exception and not the rule. In my opinion, the military should have waited until Morsi's government did something so outrageous as to delegitimize itself completely in the eyes of the world. Of course, there is peril in that too in that Egypt's institutions would have collapsed so far as to protract a reconstruction, with much suffering on the part of many. One thing is certain: if Morsi does not back down and the military does not move, Morsi will purge it of every officer with even a shred of "impurity" and this situation will have backfired. Hence my concern at the potential intemperance of this move. It is a delicate balance indeed.
Time will tell.
Could you tell me what the dynamic is between the Salafis and the MB? My understanding is they’re both Sunni, but Salafi is the extreme branch, more puritanical and MB could be called more Pan-Arabic?