Except that the 1984 public safety exception is less about protecting the public from the possibility of a threat that can happen within days and more about protecting officers from dangers that can happen within minutes.

Say that they had discovered that a bomb was planted and had found Tsarnaev. There's 5 minutes to detonate, and they manage to arrest him. At that moment they could ignore his Miranda rights and question him since the bomb has not yet been dedicated and they don't know its location; in that case, reading him his Miranda rights will cause danger to the public in a very direct and measurable manner.

When you start to expand upon the public safety law, it makes the boundaries very unclear. How far out does it extend? Is it days? Weeks? Hours? We could probably accept hours, but what if the bomb was just a vague threat? Do we deny rights based off of "what ifs" or are we going to suspend rights based on hard evidence that can be quantified.

Yes, taking the route of evidence and factual observation is hard. It will cost more lives than if you take every suspect and hold them for questioning without worrying about the consequences. Yet we all understand that at times the life of an individual, even a decent sized group of people, is not worth the greater good. The loss of a human life is something should be avoided, but when you attempt to prevent it at the cost of the rights of the living, you are not treating the dead with maturity and respect. Life comes to an end. It is the nature of the world. Sometimes that end is peaceful, sometimes that end is violent. But if the reaction to death is to pull up a shell, to cut people off from the freedom they had been promised, then all you've done is degrade the world a little bit more in a vain attempt to avoid the inevitable.