Aristotle's "Anger"

I was surprised today to read Aristotle's account of anger, in the Nichomachean Ethics, Book 2, Chapter 7:

In what concerns anger too there is an excess, a deficiency, and a mean;
and although these are pretty much nameless, let us call the mean gentle-
ness, since we speak of the person in the middle as  gentle.  Of those at
the extremes, let he who is excessive be irascible, the vice irascibility, and
let he who is  deficient be a sort of "unirascible" person, the deficiency
"unirascibility." 

That "gentleness" is the mean of "anger" is quite contradictory by our contemporary definitions, is it not?

Certainly I recall reading (I believe in The Art of Happiness) that the Dalai Lama claimed that emotions such as anger and hatred are at the core of violence; thus placing anger in the category of irredeemably negative emotions.

However, it seems that what Aristotle must be talking about here is not anger as we tend to think of it, but rather a sort of 'concern' which can be, in excess hot-tempered and in deficiency apathetic.

We are helped in this change of terminology in the translator's definition of thumos:

SPIRIT, SPIRITEDNESS (thumos): The seat of anger andof"natural courage"; it is also translated as "heart" in the quotation from Hesiod in book  I  (1095 b13). (p.315)

 Aristotle goes on in Book 4, chapter 5:

The person who gets angry at the things and with whom he ought, then, and, further, in the way, when, and for as much time as he ought, is praised. Hence this person would be gentle, if indeed gentleness is praised. The gentle person wishes to be calm and not led by his passion, but rather  as reason may command, and so to be harsh regarding the things he ought and for the requisite time.

...

For those who do not get angry at the things they ought are held to be foolish, as are those who do not get angry in the way they ought or when or with whom they ought. For such a person seems to lack perception and even not to feel pain; since he does not get angry, he seems not apt to defend himself against an attack. Yet to hold back in this way after having been treated insolently, and to overlook such treatment of one's kin, is held to be slavish. 

The wikipedia page on the topic gives us:

Concerned with	Mean	Excess	Deficiency
anger (orgē)	Gentleness (praotēs)	Irascibility (Rackham), Irritability (Sachs) (orgilotēs)	Spiritlessness (aorgẽs

Just some thoughts.