You know, if someone is trying to kill you, you don't have to let them. You're allowed to take any necessary actions to defend yourself, up to and including killing them.

In this metaphor, Russia is trying to "kill" (take over) Ukraine. Everyone including me would love it if they stopped, because war is in fact bad, but as long as they don't, Ukraine is acting in self defense, and thus supporting them is morally justified.

You would have a point if they'd both been pointlessly agitating against each other for ages. But in cases where both sides are not morally equal, arguing that they are runs cover for those in the wrong. That's what you're doing.