This article is a load of malarkey.

Being grumpy and bad-tempered are predispositions toward having negative emotions in more situations than most people would.

There are two classes of evidence in the article.

The first is evidence that negative emotions are useful in certain situations. One does not need to be grumpy and bad-tempered to recognize such situations and act appropriately.

The second is anecdotes where successful people had emotional outbursts. I assert that the outbursts did not cause the success. Passion caused both the outbursts and the success, separately. Thus there's correlation between outbursts and success but not causation.