Pauls thorn in the side, was not a disease or…

Pauls thorn in the side, was not a disease or infirmity but a messenger of satan given to him by God to keep him humble and from being exalted beyond measure… Why would God use darkness vs. Light to keep a man of God in check. How do you defend against the thought all things including darkness has its placeas well as if God is Light and cant be around sin without judgment why would he attach a fallen angel to Paul in his walk? (2Cor 12:7-9)