> The defect of original sin occurred as a result of man's rebellion against God.
Yet another design flaw. What's the point of being an egomaniacal, self-absorbed deity and producing a species specifically for the purposes of having them worship you and flatter you, if you can't even do it right?
Maybe God should have gone through a few design reviews first, yes? Maybe his configuration management system was rather poor. Or maybe he just outsourced the manufacturing overseas to India, and had some of the lower-level Hindu deities in Bangladesh slap things together.
God allows evil so that greater good may come. The greatest example of this is Jesus' triumphant death and resurrection.
Why did God create beings with free will that could rebel against him? One partial answer is that beings without free will would be robots. Beings with true intellects and wills are immeasurably greater creations than robots since they can think, choose and, most importantly, love.
Additionally, beings with free will are afforded the opportunity to experience eternal joy with God in heaven by virtue of Christ's sacrificial death on the cross. The difference between earthly suffering, and even death, to eternal life with God is like the difference between the finite and the infinite. There is no comparison.
An exhaustive yet concise treatment of the problem of evil here.