Well that goes back to what was the proper role for the southern black in the Confederate army? Some will say that this wasn't "fighting" and true it wasn't but what it did was free up 50 "white men" to carry guns and do the fighting.
It would seem that the question was approached on two levels. At the lowest levels the rank and files that the common soldier did not mind a black man fighting beside him if that black man fought. We have numerious accounts of such things happening in "unofficial" records. However on the Govermental level it was a major political problem as to the proper role of the Negro.
From the very first the problem was how do you refill to depleted ranks of the Confederate army. The southernn governmental leaders wanted this to be a "white man" only war. But with the escalation by the Union Army of replacing white regiments with Black regiments of U.S.C.T. soldiers it became appearent to the men in the front lines that the southern negro could not set idlely by on the sidelines if the south was to win its freedom.
Hence you have Cleburne's proposal and the radical part of that proposal was the proviso that slaves who honorable executed their duty were to be given their freedom. This was no different than the simular proposal that George Washington issued during the American revolution in regards to slaves that fougth in the American army.
So it wasn't such as radical idea made necessary because the Negro wanted their "freedom". I am not sure that most of them wanted their freedom. Because it would mean a complete destruction of and change in their lifestyle. To whit they would have to provide for themselves and it would no longer be the responcibility of the master to provide for their wellbeing. And that was scarey like you getting fired from your job and trying to find another.
The reason why the Cleburne proposal was not recieved was that the Gonfederate Government had backed itself into a political corner on this slave issue.