Anger is one of the passions, according to the Catholic Church. The passions are morally neutral, as they originate in flesh beyond our will. The moral value of each passion is assigned by our response to it, taking into account our ability to contain, control, or direct the passion for good.
These involuntary motions of the passions are neither morally good nor
morally bad. They become voluntary in two ways:
- by the command of the will, which can command the inferior powers of the sensitive appetite and excite its emotions;
- by nonresistance, for the will can resist by refusing its consent to their promptings, and it is bound to resist when their promptings are
irrational and inordinate. When voluntary, the passions may increase
the intensity of the acts of the will, but they may also lessen their
morality by affecting its freedom.
Anger, in particular, is taught to be praiseworthy and justifiable with proper zeal.
The desire of vengeance. Its ethical rating depends upon the quality
of the vengeance and the quantity of the passion. When these are in
conformity with the prescriptions of balanced reason, anger is not a
sin. It is rather a praiseworthy thing and justifiable with a proper
zeal. It becomes sinful when it is sought to wreak vengeance upon one
who has not deserved it, or to a greater extent than it has been
deserved, or in conflict with the dispositions of law, or from an
improper motive. (Anger)
And with respect to anger specifically, there are two scriptural passages that contrast with each other, giving us a fuller picture:
12 And Jesus entered the temple and drove out all who sold and bought
in the temple, and he overturned the tables of the money-changers and
the seats of those who sold pigeons. 13 He said to them, “It is
written, ‘My house shall be called a house of prayer,’ but you make it
a den of robbers.”
14 And the blind and the lame came to him in the temple, and he healed
them. 15 But when the chief priests and the scribes saw the wonderful
things that he did, and the children crying out in the temple,
“Hosanna to the Son of David!” they were indignant, 16 and they said
to him, “Do you hear what these are saying?” And Jesus said to them,
“Yes; have you never read,
“‘Out of the mouth of infants and nursing babies
you have prepared praise’?” 17 And leaving them, he went out of the city to Bethany and lodged there. (Matthew 21:12-17)
Now, a brief commentary on this passage: The scripture doesn't directly state that Jesus is angry. And while it actually does explicitly say so in other places, like Mark 3:5, the cleansing of the temple makes it far more clear, I think, that a zealous, righteous anger is perfectly acceptable to act on -- in rather unfriendly, uncivil seeming ways at that.
But, the mantra against anger is equally -- if not more obvious in scripture. And we hear it right from the mouth of Jesus (same guy who threw tables around):
But I tell you that anyone who is angry with a brother or sister will
be subject to judgment. Again, anyone who says to a brother or sister,
‘Raca,’ is answerable to the court. And anyone who says, ‘You fool!’
will be in danger of the fire of hell. (Matthew 5:22)
In brief, anger is an emotion. In and of itself, it's largely beyond our control and is thereby morally neutral. If aroused by zeal for righteousness, anger-fueled actions are morally good. But, the tendency for normal people to fuel our anger over trivial matters or allow it to drive us into sin is good reason to caution against anger in most, if not all, circumstances.
Jesus is effectively saying, "There's nothing wrong with anger. But, you guys can't seem to handle it. So, just try to dispense with it altogether, OK?"