Is Leighton Flowers is correct or his commitment against Calvinism destroying his comprehension of scripture?
Read Isaiah 10 and see who is right. They agree that God is saying that He is going to use the Assyrians to judge Judah for their sins by allowing Assyria to occupy and plunder His own people. And then when the Assyrians are done, God promised to punished Assyria for their sins and actions again Judah!
James White says that this passage is proof that God decreed for the Assyrians to do what they did - allowing them to do what they wanted to do and punish them for it. Leighton Flowers disagrees that God decreed the Assyrians actions but instead took advantage of their sins to bring about God's own purpose. I think the disagreement is over who gets the credit for what happened. Did God purpose the Assyrians as an instrument of his wrath and then punish them for doing what he purposed them to do? I think the passage in Isaiah says God did exactly that. Assyria was nothing more than a blunt instrument in God's hands.
5 “Woe to the Assyrian, the rod of my anger,
in whose hand is the club of my wrath!
6 I send him against a godless nation,
I dispatch him against a people who anger me,
to seize loot and snatch plunder,
and to trample them down like mud in the streets.
7 But this is not what he intends,
this is not what he has in mind;
his purpose is to destroy,
to put an end to many nations.
- Isaiah 10:5-7
I think James White is right that the reason God is just to punish Assyria because He didn't have to force them to be evil. They did what they wanted to do. Recall also that this isn't the only passage that show God working the same way. Just read Habakkuk.