Chalk it up as a case of America's inability to discuss anything with nuance, especially when it comes to historical or modern figures. As Mos Def said, "there's never no in-between, we're either nikkas or kings, we either bytches or queens."
Were the Founding Fathers saints who never did anything wrong, or were they slave owners willing to compromise human dignity and life? Was MLK a spiritual man we should all look up to, or was he an adulterer who disrespected his wife until the day he died? Nobody is one thing. People are complex, they aren't cartoon or comic characters. No one wakes up in the morning, rubs their hands, and says "ooooh what evil can I commit today!"
Kyle was a brave man who saved the lives of many of his fellow soldiers and fought for his country. He was also an unapologetically violent man who committed crimes in the name of his country. He worked hard to help vets suffering from PTSD, he also bragged about doing ugly things to his fellow citizens.
Is he a monster or a saint? Perhaps the better question is, whatever he became...was it due to what he saw and was told to do in Iraq? Does war make heroes or monsters? Can you be a hero and a monster? I haven't seen the film but the article suggests it isn't some red blooded hoorah film - it's a morally ambiguous take on Kyle. That's a good thing imo. It's time we stopped glorifying people based on their uniform and instead asked ourselves if they are living up to the (alleged) standard of excellence that uniform demands. That goes for soldiers and cops.