At least two things when we consider the paradox of God's Justice (Theodicy):
1) At the root of this question, some are tempted to use it as an accusation against a loving, just God. Paul warned us not to tread into that accusatory ground.
2) An answer to this question MUST appreciate God's prerogative and complete, righteous, holy completion of His plan that brings Him glory. "I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth†(Exod. 9:16; Rom. 9:17).
3) In the Eschaton, the angels will declare: "Hallelujah! Salvation and glory and power belong to our God, for true and just are his judgments. He has condemned the great prostitute who corrupted the earth by her adulteries. He has avenged on her the blood of his servants."
This answer to this question is not based in our ability to explain how God takes pleasure in evil. The question is answered when we consider that God's plan is Righteous, Just, Loving, Gracious and ultimately brings Him glory.
This is not unlike the Imprecatory Psalms.
Calvinists have the best answer for this question. Otherwise, having a perspective that could charge God with being unjust is what Paul warns against.