Debate Over Tsarnaev's Rights

I have seen commentary about whether or not Dzokhar Tsarnaev should have been given his "Miranda Rights" immediately or not.  On one hand, there are those who say that the "public safety" exception where questioning can proceed without Miranda warning where "police officers have an objectively reasonable need to protect the police or public from immediate danger."  Although the Supreme Court has carved out this exception, I think it requires modification to protect all citizen's rights.  If the police have need to invoke the exception, any evidence obtained should not be admissible.  In this way, the police won't be tempted to stretch the limits of the exception to the breaking point, while still giving them the opportunity to act in the interests of public safety.