A film glorifying him seems to be in bad taste (I didn't see it), but at the end of the day I do think there's some merit in the argument that soldiers set aside morality and ethics on the battlefield and just do what leaders tell them to do. Chris Kyle didn't start the war; he didn't invent the position of sniper, he just did what he was called on to do, and he was very effective at it.
His complete lack of anything remotely resembling moral self-reflection in his life after the war zone surely is not universal of snipers.