There's a classical dilemma in ethics you've likely heard of that's known as the lifeboat problem. Imagine that you're on the last lifeboat on a sinking ship. It's already full beyond safe capacity. The chance of rescuers arriving any time soon is minimal. There are still passengers in the shark-infested water who have little chance of survival if they are not pulled out. Those on the lifeboat have a choice between leaving them to almost certain death or taking the chance of very likely sinking the boat, with all lives lost. What do you do?
There is no unique "solution" to the lifeboat problem because neither action is something a moral person would want to do. The point of posing it is to 1) make clear that not all moral choices are black-and-white and 2) to think about how we make moral choices. When faced with a dilemma, we should do our best to realistically assess our options and consciously choose to do what we believe to be right based on the best information available. We cannot settle for adopting a simplistic view that makes the choice seem easy. Moral decisions can only be made after considering the likely consequences of our actions, rather than responding rashly out of emotion.
The typical first reaction when faced with the lifeboat dilemma is to want to try to save those who are about to die. If you don't consider the risk that poses to everyone in the boat, you could kill them all without even realizing that was a possibility. Some would be willing to take that risk, hoping for that by some miracle that all survive, but most of us would want to save as many as possible. Logically, given the facts as presented, that would be accomplished by letting some drown, as horrifying as that prospect is. You might decide to try to take as many as will fit on board and tell yourself that you are "leaving it up to God" whether anyone survives but in reality, you are still responsible for your choice.
The situation in Ukraine can be considered a corollary of the lifeboat problem. If the US and other NATO nations quit supplying Ukraine with weapons, Ukraine would face certain defeat. However, if NATO continues to send weapons it is risking the lives of everyone else on the planet due to the ever-growing threat of nuclear war. As an additional twist, some contend that a Russian victory would embolden it to make war against the rest of Europe. Others doubt this, arguing that Russia's defeat would be worse because it would allow the American Empire to continue to advance, unchallenged, its bloody plans for global domination.
If your goal is to minimize destruction and loss of life, the choice is clear. Even if you believe that Ukraine has a fighting chance of driving Russia from Donbass and Crimea, this would clearly come at the cost of a great loss of life on both sides, and Ukraine would be left in ruins. If you don't believe that Ukraine has any hope of defeating Russia on its own, it's clear that further resistance will only result in more death and suffering on behalf of a lost cause. In either event, the only way we might help stop the carnage is to demand a cessation of weapons shipments and call for the US to support negotiations.
Calling for negotiations alone is a feel-good response with no chance of affecting the prospects of peace. Russia cannot realistically be expected to negotiate while Ukraine continues to receive ever-more powerful weapons from the US. And after the enormous costs in blood and treasure that it has paid, there can be no retreat. Putin knows that after the betrayal by NATO and Ukraine of their promises in the Minsk Accords, Russia does not have a viable partner in negotiations. Until NATO shows good faith by halting the flow of weapons to Ukraine, it will continue its grim task of grinding down Ukrainian resistance in a war of attrition. With more than 200,000 fresh troops scheduled to deploy soon and four times Ukraine's population to draw from, it's clear who will win such a contest.
The only rationale for supporting arms to Ukraine as things stand is to believe, against all reason, that Ukraine can not only push Russia back to its pre-February 24 position but retake Crimea. Whether such irrationality stems from a real fear that Putin has the desire and capability to take over Europe like the (latest) modern-day Hitler he is painted out to be, or from an atavistic desire to see the guys in the white hats beat the guys in the black hats, it's time that those "peace activists" pushing for more weapons to Ukraine face reality. It's not our moral responsibility to enable the Empire's proxies to fight Russia to the last Ukrainian. Even if Russia were miraculously defeated decisively on the field, what then? Are they so determined to "win" that they're okay with nuclear war?
The choice is clear: Those who have a genuine interest in the welfare of Ukraine and the rest of world must demand that their governments end weapons shipments to Ukraine now, and that the US encourages negotiations.