I believe also that the scripture in Romans sums up so well....
Satan is a vessel God has used since the dawn of human time for His purposes. We must remember God has always, and will always be in control.
He tossed out satan and his minions but He was not done showing them the error of their ways. In fact, He used what was meant to harm and made it beautiful. He did it all with Christ.
And we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose.
Romans 8:28 NASB
Iniquity was found in satan and in us as well because of his deception. We like the dark one, were given a choice. I think that alone shows God's goodness, especially when we see that He sent His only begotten Son to redeem us.
We mustn't ever forget that any dark or evil thing, God can and will use for His purposes...
Let me say... Holy Master, thank You for Your tender-mercies and for Your patience as we come together to reason. Your ways are not ours, nor are our thoughts Yours. Please forgive me, if I have it wrong. I never want to put you in a box, or speak with arrogance, assuming I understand You. I know You are all good...pure truth, power, love, justice and righteousness; I reach my soul to only You. If I have said anything foolish or in error, please forgive my ignorance on Your Matters. Thank you for all Your ways, to You I bow.