(Note: this post is an edited form of a Facebook status I had written earlier, hence the somewhat less polished form)
Short version: Einstein said that repeating the same thing, over and over again, while expecting different results is the definition of insanity. And to answer the utterly exasperating question of "are you suddenly an expert on the subject" by way of a somewhat silly analogy: you don't have to be a medical expert to know that you won't cure someone's broken arm by pushing him off a roof or breaking his leg.
Historic Pattern: Using force against sit-ins since 2011 in the experiences and eras of Mubarak, SCAF and Morsi always resulted in the SAME result: more people joined, they became more violent and confrontational and less willing to compromise, a stain glued itself on the legitimacy of whoever was in power, and (in many cases) people sympathised with those who were the subject of the usage of force (especially as most Egyptians are still politically independent, non-partisan and non-ideological), and sizeable political problems ensued internationally as well. Then, most importantly, there was almost always a human "tragedy" that left an indelible scar on our consciousness. Lives were lost, people were injured, and judicial due process never yielded any satisfying results. Add to that: the police's record on how it tactically handled most protests or sit ins since 2011 leaves us feeling more tense than comfortable.
Conversely, as one example: on the other hand, every time a sit-in was left alone, and the political process moved briskly along at the same time (whether the political transition was moving fast on its own or there was some form of a dialogue going on), such a sit in eventually ended or lost much of its steam or momentum until it became a non-factor.
This situation is one of the most complicated since 2011, if not the most. It is quite volatile, volcanic and sensitive. The way it is handled will strongly affect the stability, image and future of Egypt, locally and internationally. The situation has to be contained, the political process has to move along, and surely any violence or transgressions perpetrated by the demonstrating side should be dealt with decisively, according to the law and international standards. Meanwhile, the pro-Morsi side needs to reevaluate where it truly stands right now, what it actually can and cannot gain, and - if the protesters remain in their sit-in for a while longer - how they can make the lives of people around them in the area immediately safer and easier. And yes, what I am writing here sounds too idealistic given the ground reality, but someone has to write something that is at least a bit idealistic.
(Bonus Blog Note: the Muslim Brotherhood should note that it is a form of child abuse to make children wear burial shrouds and go on demonstrations as such. Better yet - to all sides in Egypt - keep kids entirely out of politics. Let them be, you know, kids.)