Because you have not studied religion and witnessed humans at work like an experienced person capable of issuing such binding decrees. You should issue an apology for your crude remarks. Even Khawaja Asif showed more class with the wannabe Shahanshah, King of Kings, a very blasphemous title. It's like that Ethiopian who claims to be King of the Jews from Solomons lineage and has DNA tests to show for it.
It is a legitimate decree that weapons of mass destruction are forbidden in Islam. Killing one unjustly is murder of whole mankind.
Mr. Khamenei is only guilty of expecting good from humanity. He offered the only thing a Muslim can offer freely, honesty. It is an entire different discussion that are Muslims pious enough to follow his verdict or will they go astray.