Are you aware of any case where the US went to war under pretenses known to be false from the start, or interfered in the internal affairs of another country to cause loss of life, or allied with countries that committed terrorism against the US and others, etc. and none of the initiators suffered any consequences?
It's bad enough that morals can be twisted enough to justify just about anything and in any condition, and education these days lets anyone think they can justify anything simply by the fact that they said it. Don't add hypocrisy to that too.
Of course, I do. Not to say I don't have biases, or that I'm always have an access to 100% correct information. Life's not that easy, of course, but it still doesn't mean that it's always blurry, relative, and let's do nothing as your nihilist approach suggests.
It only ends when one side or the other, and anybody who might have empathized with them, is completely annihilated or when somebody stops behaving, from their perspective, righteously. Neither option is probable, which is why society just keeps replaying history on an endless loop in history, with little more than technology offering a change of scenery.
If you want to see what will happen tomorrow, simply learn about what happened yesterday. The only trick is realizing what role you're playing.
The countries with potent military capabilities dictate how everything goes in this world. It was true a thousand years ago, it was true a hundred years ago, and it's true today. It will always be true, for very obvious reasons.