Knowing the outcome has nothing to do with whether God should or should not be angry it is a manifestation of his sovereignty.
That is one reason why there is so much debate over what we are capable of in contrast with God being in control of everything. People do not easily see the victory and liberty we do have that is in alignment with what God knows before hand.
Gods anger to us is this teaching that he is going to get us all, when it is an action that is according to his standing counsel.
The Cross of Jesus Christ is a result of Gods anger. That Cross , its work, is a part of total restoration. Gods anger is not about man inducing self righteous guilt upon one another, it is an anger that destroys evil, corruption, breaks the chains of bondage, raises the dead, frees us from addiction, softens our hearts, causes us to repent, causes us to love.
Welcome his anger.