I think we should supply them. Why not? Just because Putin doesn't like it, we shouldn't? I'd say that's exactly why we should. Putin's rage (and the warnings he subsequently issues) always reveals his plans. Giving the Ukrainians missiles raises the cost for Putin of going forwards with a coastal invasion and turns his inflexibility against him if he does.
Russia needs to get the hell out of Ukraine. That's all there is left in this situation.
Then let Ukraine adopt the neutral posture it has offered. Neutral but defensively strong, not neutral but weak. And let it act as a useful bridge between Russia and the EU, economically-speaking, so there's a path of peace and recovery for everyone over the next few decades.
As to Russia, hopefully they will somehow find new leaders once they learn what a disaster Putin has been. It really needs to figure a way to befriend its neighbours, instead of bullying them. If it can't manage to do so for humanitarian reasons, maybe it can figure out that it is more efficient to cooperate some. A prosperous, independent, peaceful, law-abiding Russia would be fine with me. Influential because it is a model, not because it has artillery.