Sorry, I got a little too militant there for a minute, haha...
No worries. Look, I'm almost absolutely on page with you about war (I can't think of one the U.S. has engaged in since the Civil War I can say that I would support), I just take a more nuanced attitude toward the use of violence and the making of war, I'd say. Violence can be tactically advantageous in a given situation, but it should only be used (a) to free someone or a group of persons from an outside oppressive and controlling force and (b) when you're sure you can use it to win.
I tend to think that it's okay to kill people who hold other people as slaves, or exercise absolute tyrannical authority over people, but that's just me, and I think that's a fairly sane position.
To fight and to kill are two different things, there are ways to oppose tyranny without killing anyone.
If people have a right to life, then killing them is wrong.
No, there really aren't ways to oppose tyranny without removing the source of said tyranny. You would never be successful in kindly, gently asking the slaveowners to free their slaves. They
had to be exterminated or rendered incapable of exercising their power to purchase and hold slaves.
I do not intrinsically hold that all life has value or that life should be placed upon a pedestal or any of that, either. I think that doing so is a mistake and causes a lot of undue suffering in the world, precisely because such thinking leads to the kind of thing you are arguing here.