So to follow your logic, you believe that empowering a convicted rapist with full rights today, will protect you tomorrow from a tyrannical majority, who will criminalize your religious faith, but respect a previous law that allows such criminals to be armed?
Sorry, but that is not quality head work.
And sorry, but if "shall not" applies to everyone all the time, no matter their felonious actions, then you are going to have to allow inmates to carry guns in prison. There is nothing in the Constitution or common sense that limits punishment to incarceration.
Disassembling your straw-man there is no Constitutional right to rape...
You want an exception to the 2nd? Amend it.