"The reason Iran is beefing up their defensive capabilities "

NUCLEAR WEAPONS ARE NOT DEFENSIVE.

ABM systems ARE.


With nuclear weapons, one can only destroy the enemy. Since they ARE WMD, they are most effective agaist cities and civilian populations.

ABM systems CANNOT be used against cities- they are specific to attacking MISSILES THAT HAVE ALREADY BEEN LAUNCHED.


Claiming the ABM systems are aggressive, and nuclear-armed missiles are defensive is not a reasonable arguement.