The purpose of moral judgment is to short-circuit reasoning and save the
work of thinking. That's why radioactivity is intolerable and trolley
problems are intractable; people are unable to think about them. Cluster
munitions are the same. I have not seen any source attempt to judge
whether the lives lost to future danger are more or less than the lives
saved by shortening the war.
clue:
Biden appears to know it. He gives precedence to the moral argument (the
Ukrainians choose this tradeoff themselves and it affects only their
territory) over the practical argument (it is the only way to alleviate a
munitions shortage in the short term).
Another purpose of morality is to improve conformity, and therefore
cooperation, among an in-group. Notice how people blame Americans, not
Ukrainians, for a choice that Ukraine welcomes and America made
reluctantly. Ukraine is in the out-group.