Arminians have often claimed that if God did not allow people the freedom to sin, then we would be in a forced relationship with Him and would be little more than robots. Thus the Freewill Defense is used to get God "off the hook" for the evil that exists. Namely, God must allow evil to occur in order for Him to have the chance to have a real relationship with His creation. Let us assume this is true for the sake of argument.
Jesus said: "You have heard that it was said, 'You shall not commit adultery.' But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart" (Matthew 5:27-28). Additionally, it can be argued that while 9 of the 10 commandments deal with external behavior, the 10th commandment ("You shall not covet…") internalizes all of the previous commandments as well, such that sin is not simply acts that are committed but also includes evil thoughts.
This means that sin need not be acted out in order to be sin.
This causes an immediate problem for the Arminian's Freewill Defense. Namely, evil occurs even without the actualization of that evil. Thus, when a murderer decides to kill someone, he has already sinned. If a rapist decides to attack a woman, he has already sinned.
But if sin already exists, then God has no need to allow the actual behavior to occur in order to keep people from being robots. Simply put, God could cause the knife the murder holds to dematerialize, or He could cause the rapist to become neutered. This would stop the behavior from occurring, but would not in any way violate the will of the one who would have engaged in such a behavior. The evildoer would have still wanted to do evil and sin would still have occurred, but there would be no other human victims involved. The sin would remain solely between the sinner and God.
Add to the fact that if we see someone trying to murder or rape another person, we are morally obligated to intervene to the best of our abilities to save the victim (and note, when we do intervene successfully, the guilt of the person who attacked the victim is not mitigated), then it becomes obvious that the Freewill Defense is sorely lacking. There must be some other reason for God to decree/permit/allow evil actions to occur.
[Note: A Helmet, we know you'll just say "it's not the greater good defense" without giving anything else, and since I could practically write your comments already, although with better grammar than you use, you don't need to respond here.]