Love is not some insipid woolly emotion offered to everyone in the same way irrespective of their response. Love is passionate. Infinite love is infinitely passionate.
God’s love has content.
He truly cares about us, and more than that he truly cares about the honor of his name and the glory of the trinity. God’s love is primarily turned towards himself as the most lovable being in the universe. For all eternity the Father loves and is satisfied in the Son, the Son loves and is satisfied in the Father. They both love and are satisfied in the Holy Spirit, and he also loves and is satisfied in them. Such love in such a holy being is also the source of wrath.
Imagine if you will that someone you love dearly is murdered. It is right and appropriate that you would feel anger. It is understandable that you would seek justice. As a believer that very impulse must be tempered, however, by the instruction to leave the due repaying to the one infinitely more wronged. “Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, “Vengeance is mine, I will repay, says the Lord.” (Romans 12:19). We turn our wrath away by the sure and certain knowledge that someone else is wrathful on our behalf.
As finite beings, there is so much sin in this world that if we allowed ourselves to be wrathful at it, anger would consume us and there would be nothing left. Bitterness does precisely this to man.
But God is not carelessly indifferent as some imagine him to be. God’s anger burns with a holy fire precisely because he loves. It is not that love and anger are set against each other, and that somewhere in the middle a lukewarm God is forged. No, God is wrathful because it hurts him to see the destruction sin has wrought in the ones he loves.
He is angry because sin corrupts the world he cares for. He is angry because sin warps the way people see him. He is angry because the honor of the God he loves is trampled in the dust. His love for us, and his love for himself requires him to act. He is angry because holiness and justice, being in his very nature, must be vindicated or he would no longer be God. He cannot simply overlook sin and remain God. Or not the same God he has always been, anyway.
The whole argument of Romans is that God is faced with a dilemma. How can he be just and the one that forgives sins? It is only in the cross that a solution to this is found. It is not that Jesus saves us from an angry God. He himself is angry at sin. He is both the refuge and the one from which we must run. He chooses to offer us a way out. Then he warns us, that since this is the only way out, if we trample all over the offer, there is nothing left for us but wrath.
“Serve the Lord with fear,
and rejoice with trembling.
Kiss the Son,
lest he be angry, and you perish in the way,
for his wrath is quickly kindled.
Blessed are all who take refuge in him.”