I think, this is in part a consequence of the deification of Steve Jobs, who might have adopted a similar stance towards his partners/employees. Such behavior is now automatically assumed to be acceptable by some subset of people. The No Asshole principle is passé. The author may have written such an email irrespective of Steve Jobs influence. But the audacity to post it on his own blog for everyone to "admire" certainly has to do with the publicity around the Jobs' supposed douchiness.
I think that's probably ascribing Jobs too much credit. He certainly wasn't the first businessperson with a superinflated sense of self-importance and a serious disregard for the well-being of those "in his way", even when those people are his employees.
But he was the first one to use that self-importance to build the richest company in the world. Most of the stories about people like that end "and then all the good engineers quit so they didn't have to put up with him, the products started sucking and the business went down in flames". Steve Jobs avoided that somehow (probable by having really, really good judgment), but imitators don't see that part, they just see "self-importance works".
