: As for a good term for what they bare doing...

: Cultural chauvinism doesn't work either but I don't think it matters if we
: don't have a sound bite phrase for it.

: Cultural blindness? arrogance? parochialism? cluelessness?

Parochialism fits, but TVTropes suggests "Creator Provincialism". It's not quite blindness, it's not quite arrogance, it's just an extension of "Write what you know". If you've grown up in America watching American television shows, you're probably going to be writing Americans in America.

: I really have not made my point clear.

: I'm trying to say that dudebros will not go down well outside of America. I
: also mentioned that they probably wont go down too well inside America. I
: am saying that 343i is blind to tone.

Oh, I'm not going to argue against that.

: I am also saying that they might not even have realized that the rest of the
: world isn't America or that they don't aspire to be Americans or,
: specifically, dudebros. It could rub people, especially non-Americans, up
: the wrong way.

Seriously, what's the difference between a dudebro and a chav? They're both middle-class white trash with an (overly familiar?) manner of speech.

: But do they make good heroes? Would you aspire to be one?

Not all heroes are people you want to be like. There are some characters who have monumentally screwed up, but their laudable action is in recognizing that they have committed wrong and fessing up to it.

: Is it a great concern of yours that mass murders find a way to feel good about
: themselves again?

It's not about feeling good about oneself. Contrition and atonement rarely leave the subject feeling anything more than regret.

: The Arbiter did it by putting all the blame on Truth and
: then killing him. It's not an honest thing to do but most people lies to
: themselves when their self image is at stake.

Did he? From what I remember, killing Truth was simple revenge for the genocide that the Great Schism unleashed.

: The ones who don't lie to themselves tend to suffer from depression so it's a
: mental health issue. :-)

*Twitch*

: 343i have stated that he was in overall charge of the forces at Reach and
: that the strategy used was his. They confirmed that his role of Supreme
: Commander meant what it sounds like. They also state that he is
: responsible for the destruction of 7 planets and the deaths of over a
: billion humans. So he wasn't, "just a soldier".

Which is a great start, by the way.
Thel can't lay all the blame at Truth's feet for the war. The Heirarchs may have started it, but Thel and his fellow Kaidons kept the war going. They honestly believed that their religion justified the extermination of an alien race.

If the Arbiter tries to use the Heirarchs and the Covenant religion as a scapegoat, we'll know that he's learned nothing. But if he really tries to atone for what he did... well, it'll be interesting to see how he balances that with his duty to lead the Elites in a time of war.