You painted a sad but true picture of a rogue state.
If we had any integrity maybe we could have just publicly retracted our participation in the Geneva convention if we don't want to follow it.
No, "we" don't want to quit Geneva conventions because "we" want others to follow them when some of our soldiers are captured by the enemy. There was a lot of noise made that Iran took a picture of captured UK sailors "in violation of Geneva conventions." (I guess next time Iranians won't bother to prove that they treated their detainees well.)
The question is whether there is even a point trying to live up to a standard of morality and ethics in foreign relations
On an individual level everyone should live up to a standard of morality and ethics. Otherwise bad karma will bite you. Not in a religious sense; gods rarely interfere in human affairs (except FSM, who is always nearby, tweaking your measurements :-) Bad karma comes back just as a reflection of your own bad actions. Sell drugs, be killed by another drug dealer. Go shoot some "brown people" - don't wonder why you got shot up yourself. That's the primary mechanism of karma, and it works very well.
On the national level ... well, accept the fact that you, as a citizen, have no control or even influence over political decisions. You are nothing but a worker ant whose only purpose is to make war materiel for your masters. Humanity knows of only one way to repair the damage; it's in the fourth box at this point.
I would rather live in a country where we had more expensive gasoline than one where we try to be the biggest bully, but maybe I am just naive.
Consider the option of Canada, if you are not afraid of -20C temperatures (at best) in winter. As the exodus picks up (for many reasons, political being the least important) the immigration rules will be tightened. At least you will stop financing killing people all over the world. As things are, you are "running with a machine gun and shooting brown people up" for about two months per year, considering your tax share and the percentage of taxes that directly and indirectly go to the altar of death. You don't have to be a grunt with a rifle; your hands are just as bloody if you buy ammo for the grunt, or even food, so that he can do his job in comfort. Every US taxpayer is guilty of that, and every US voter is guilty of electing a member of the War Party to the throne.