Using cluster munitions has consequences, not using them also has consequences. This is a trolley problem with 2 shitty outcomes. However the people who have the most information, the most to gain, the most to loose, and have to deal with the ongoing consequences believe that adding cluster munitions to the arsenal is the best option. They have weighed the consequences of using them against not using them and they’re going to use them.

you've spent a bunch of time complaining that i'm being uncharitable to you (even though i'm using direct quotes from you and logically following from those quotes) and you're again demonstrating what i mean here in different words. if they weigh the best option is to begin executing Russian soldiers—a thing they could do at any time and which under your premises you have no way of calling unjustified—how can your position here be anything but explicitly in favor of that? your position here outsources the entirety of itself to what Ukraine thinks should be done, and leaves no outs for what you think isn't moral if Ukraine starts doing such things!