Here's why your friend is a.misguided fool and feel free to use this: as a leftist your interest when war between two bourgeois powers go to war is primarily to minimize the amount of working class people being killed because they are the clas you're attempting to uphold. This means that the war and therefore killing ending earlier is better so aside from not having a war in the first place the fastest route to peace is the best route. In this case that is Ukraine's surrender, doesn't need to be unconditional and could probably have been more conditional earlier but at the end of the day every way ends at the negotiation table and Ukraine's power at that table has only lessened.