Well, the Catholic Church is always willing to cut a deal, even on the Seven Deadly Sins, so let's say....<counts soul points> how about much less wrath, a little justified anger, and we'll call it a minor transgression, okay? Take 10 Hail Mary's, a few Our Father's, and see if you feel okay in the morning.
Expressing one's anger in a reasonable manner is a good thing for the spirit, but taking it too far is a different kettle of fishes and loaves entirely.
Now here is a question: say you are in a committed, proper Christian-style relationship, and you get into, let's say, a mildly wrathful fight, then make up with kindness (your sin therefore being absolved) and have wicked lustful sex (which is a kindness) afterwards, which results in a presumabely god-blessed pregnancy? What then, pray tell? Would you give birth to Damien, Prince of Darkness? Yeah, okay, it's the make up sex thing again, but all you would have to do is say a little forgiveness prayer, stay off the wife for a few days, and all would be well in the world. Anyone know that commercial: "If life could taste as good as Swiss Chalet?"