One of the things which I think people are having a hard time comprehending, Russia are less and less playing by the rules, I support arming Ukraine with anything not prohibited by the Geneva Convention, Russia has less and less compelling them to abide by such conventions.
Which comes back to my post above - we need to be mindful of such aspects when aiding Ukraine, that isn't to say we shouldn't be doing so but we need to be prepared that there may be consequences and ready for them - there seems to be far too many people thinking "but Russia won't/can't do anything".
EDIT: To be fair one the one hand the UN has always been about getting people around the table talking, on the other hand it is utterly useless in a situation like this.