The way I gloss it is this: if you're a spirit you don't encounter resistance; you can fly about, pass through walls; you don't age, you don't get ill, you can't hurt or be hurt; none of the things we call "evil" exist for you. But if you descend into matter you meet resistance on every side, your body is vulnerable and needs feeding, resouces are limited and you're having to compete to get them. Another way of putting it is that evil arises out of difficulty.
No difficulty, no evil. But no adventure either, no cut and thrust, no extreme emotions, no excitement. Life on earth comes with evil- so-called- built in. Without evil life would be like the perpetually sunny, white picket fence existence Jim Carey endures in The Truman Show- and who wants that?