I would say that at the level of decision making "macho arrogance" is only rarely an important causal element. Most capitalists and their political poodles are fairly rational in their decision making. But in various forms (and in the U.S. above all in the form of white racism) such arrogance is an essential part of the imperial project in two ways: (1) it informs the efforts to make such slaughters as Vietnam "palatable" to the public and (2) it enters into the morale of the "middle managers" of the empire: the career diplomats, the career officers, the prison wardens, a goodly sprinkling of corporate middle (and even upper) management, and (yes) the professoriate and other professional intellectuals of empire.
This is why the fight against racism has to be a core element in class struggle in the United States. And this is also why it is important to see "racism" as an ideology with a material base in the continuing material conditons of life of (above all) African-Americans, not as an independent causal factor with (as they say) a "life of its own." This is why, in so far as "non-majoritarian" struggles in so far as they do improve the living condition of black Americans *also* undercut the material basis of racism and *therefore* undercut the propaganda rationale of empire.
[Incidentally, none of the "ideas" in this post are even remotely "original" with me; they are a condensate of an immense reading list filtered through my own experience in the anti-vietnam war, central-america solidarity, and anti-gulf war struggles. The whole argument is quite commonplace, but not for that reason often in the forefront of the consciousness even of those who accept it.]