I agree with you to a point: no matter the sin, the blood of Jesus can cover it and forgive the sinner. However, even before we are saved God restrains us (by our conscience, circumstances, etc.) in the degree of evil that we perpetrate. I believe that people whom God allows to go so far into evil (raping children, mass murderers, etc.) are those "vessels of wrath prepared for destruction" but I cannot say with authority that there will be no former cannibals et al among the redeemed at the end.

Romans 9:22-24 "What if God, desiring to show his wrath and to make known his power, has endured with much patience vessels of wrath prepared for destruction, in order to make known the riches of his glory for vessels of mercy, which he has prepared beforehand for glory— even us whom he has called, not from the Jews only but also from the Gentiles?"