Saying Israel is not an ally because they have spied on the US is an obviously false argument considering that the US just like most other countries spies on just about every country in the world. The article itself talks of the US spying on Israel and other allies.
Another question to ask: Did his actions actually have any negative effect? Even if information was given to the Soviets, that doesn't mean actual harm was caused other than America losing points in the intelligence game of the Cold War. Also, legally, can the government go back on a plea offer? What did they offer him that persuaded him to plead guilty? Or was he stupid enough to plead with no actual promise?
It's not up for him to decide which secrets foreign countries should receive. It's up to his superiors, and it's his job to ensure that their decisions are put into place.