You don't see the difference between killing a Saudi diplomat and innocent people versus killing a terrorist on a kill list? Good grief.
As for our predator strikes to kill terrorists, we take out plenty of tag-alongs too.
The Saudis have been terrorist enemies of Iran for quite some time. If Saudis are on Irans kill list, as they have defined their enemies of their state, then the same argument you make for our terrorist kill list applies to their terrorist kill list.