Right livelihood - how many cutouts is enough? Slaughtering an animal for meat or a  person for wealth is not right livelihood, nor is it right to pay someone else to do so. So far, so good.

Modern corporations allow individuals to amass more wealth and power than Genghis Khan while not having to lead the charge from up front. 

It's easy and direct enough to link Genghis Khan to the invasion of Eurasia, but it's nearly impossible to link a billionaire to a war in Iraq or Congo, though it is common knowledge that the modern economic system since colonial times promotes wars in natural resource rich parts of the world  all the time for economic gain. 

The billionaire beneficiary is often on a yacht thousands of miles away, while ordering the war through middle men, board room decisions, corporate interests, political lobbyists and hedge funds.

Such specifically designed to be tenuous connections to the scene of the violence allow the shot caller to even forget there's violence.

Kind of like how when people pick up shrink wrapped meat in a supermarket it's a very different sterile experience from going out into the backyard with a cleaver and a cackling hen and returning with bloody hands.

Even in his time the Buddha did not criticize wars or say being a king isn't right livelihood. So where's the line in the sand, how many intermediaries does it take to make the wrong right?
As I understand the Buddhist approach to ethics we are all responsible for our own actions, and the Buddha defined significant actions as "intention" (AN 6.63 cetanāhaṃ bhikkhave kammaṃ vadāmi). It is the impact of our intention that is under our influence (control would be too strong a word).

How well we understand something like the food chain will be dependent on how much effort we put in. Clearly meat always comes from dead animals. More subtly we know that animals are often mistreated in the production of food. So free range eggs most likely involve less cruelty than battery eggs. Diary products always involve killing off most of the male calves very early, and rennet for cheese often comes from the stomachs of those same calves. A little research can reveal much about such things.  But ignorance is also a karmically significant intention, especially if it is based on laziness or deliberate shying away from the truth. Intending to remain ignorant so as to continue to enjoy a sensory pleasure is an unskilful action. 

On the whole we have little influence beyond our own actions. We may have some influence on our intimates, but even that is limited. The point of application of Buddhist ethics is our own mind. We certainly have little influence over billionaires. But then the theory of karma supposedly takes care of this. We take care of our karma and karma takes care of the problem of the actions of others. Everyone gets the fate they have worked towards. The multi-life perspective allows for localised unfairness to persist because the afterlife sorts out the discrepancy between action and reward/punishment. 

Of course these ideas of morality were conceived in an environment with very short food chains - most people probably knew the source of their food. The rich directly exploited their serfs for wealth, but this was pretty much out in the open.

And of course bhikkhus (literally "beggars") made a decision to accept whatever food they were given, excepting only when they knew that an animal had been killed specifically for the. So the bhikkhu purposefully distances themselves from knowledge of the food chain and accepts whatever comes. The morality of this seems moot from a modern point of view. Accepting alms from someone who is am arms dealer for example, would seem to be unethical. 

I'm not sure it's true that the Buddha did not criticise war. He did tend to stay out of politics. But for example in the opening pages of the Mahānibbāna Sutta he subtlety dissuades Ajātasattu from attacking the Vajjis. And keep in mind that the tradition says that Ajātasattu had already tried to assassinate the Buddha. in any case the Buddhist texts are unequivocal in denouncing violence. And war is only violence on a larger scale.