Why exactly is there this sense in business in the United States that you have to be an asshole in order to be successful?
That's mostly a rhetorical question, of course.
However, here is some evidence that cranky bosses are not good bosses from Sigal Barsade, an associate professor of management at the University of Pennsylvania's Wharton School, and Donald Gibson, an associate professor of management at Fairfield University's Dolan School of Business in their paper, "Why Does Affect Matter in Organizations?" in Academy of Management Perspectives:
Looking at studies of large companies and small companies, companies run by women and by men, their conclusion is clear. "The evidence is overwhelming," the authors write. "Expressing positive emotions and moods tends to enhance performance at individual, group, and organizational levels." Employee moods, they find, affect just about everything anyone does at work—job performance, decision making, creativity, turnover, teamwork, negotiations, and leadership.The authors of the study encourage managers to regulate their emotions. :)