If Russia is dashing itself against the rocks of Ukraine's defenders, its fewer orks and tanks that can roll into Canada.The main point is that the left is opposed to Russia winning. If they have to keep fighting, it weakens Russia.
Russia has been a net negative on global stability, and supports conservative/right wing politicians all over the world. The fall of Putin means a more progressive world. Keep arming Ukraine. It means my family is less likely to get drafted into a future conflict.