A) If only it existed,

B) Free will doesn't mean evil people have to be allowed to kill good people. Separation, objective or detectable measurements for evil, answering prayers, helping evil people who want to be good be good (since neither prayer nor religion decrease the recidivism rate.

C) Free will doesn't mean evil has free reign. The God in the Bible, for example, interacted plenty of times to stop evil. Why doesn't this god do that? I don't think any answer is morally satisfactory for an omnipotent being.