Kinda off topic but other side of the coin, befriending the asshole: At my first job there was this grizzly old engineer who was known for being pretty surly, but knew the code base almost as if by memory, and the behavior of the code. He was bothered by anything and everything and really just wanted to run out the clock and go home and work in his wood shop. I was in support and nobody wanted to go to him for help,…
Not a native speaker but shouldn't grizzly above be grizzled? :)
In common use, though, "grizzled" is generally used to imply "old" or even "unkempt", and "grizzly" is generally used to imply "bad-tempered" (probably alluding to the behaviour of the "grizzly bear")
..in this case, according to the story, either word would apply!