The essence of idolatry is the belief that G-d is not the only power influencing life. Idolatry doesn’t preclude G-d’s existence; it is the mistaken idea that there are other gods or spiritual entities that have powers, and therefore it is beneficial, or mandatory, to pray to them and worship them in order to gain reward.

Anger presumes this same belief.

About G-d it is said that “there is nothing besides Him.” G-d is everything and everything comes from Him. Simply, this means that there are no other deities. Jewish mysticism teaches that everything that happens is directed by G-d. Even a minute occurrence, such as a leaf falling from a tree, has behind it G-d's intent and purpose. Nothing is arbitrary. So, if even a falling leaf is directed by G-d's will, then surely everything that happens to a person is directed by G-d. G-d—and He alone—is the Source of everything that happens to us.

With this principle faith in G-d as our base, let's find a real life example that can test this faith.

What if someone would make a very insulting remark to you? The “natural” reaction is to become furious. But by becoming enraged, the person is forgetting that hearing an insult is also directed by G-d. He denies that G-d sent someone as His messenger to say those cruel words.² An angry person "shoots" the messenger, and negates Who sent him (needless to say, he forgets to contemplate the message that G-d is trying to send). Such a person denies that G-d controls everything; he believes that the person who insulted him could act totally independent of G-d. He grants his insulter autonomous power, free of being G-d's emissary.

People get angry at a boss who refuses a request for a promotion. They are furious at the lady who “stole” their fiance. They are fuming at the driver who cut them off in traffic, and the salesman who didn't give them back enough money in change. These are all very natural reactions. But they are very subtly denying the fact that G-d directs their life, and not all these human offenders. (Please note that while all these happenings might seem to be to a person's detriment, "no evil descends from Above"—G-d only causes things to happen which will benefit us even if we cannot yet perceive this.)

Anger is the denial of G-d being the sole Source of everything, and the admission that other people or powers have independent existence and influence over our lives. Thus, the kinship to idolatry, and the reason anger is “anathema” in the eyes of G-d.