why does justice murphy believe that there should be limits to military discretion in cases such as these?

His belief was for the protection of constitutional rights of citizens.

Explanation:

The Justice Murphy dissent was relating to the case between Korematsu vs United States on civil rights of some disloyal Japanese group.

Murphy assertion was that the exclusion of both the alien and non-alien from the pacific coast should not have been granted to the military to carry out. He states that the exclusion granted makes the military looks above the constitution.