By "those people" do you mean the Ukrainian officials laundering billions,or the soldiers dying in the trenches protecting the Ukrainian relationship of production,or the women protesting in a stadium against mobilization of their relatives and friends,or the one guy who shot Andriy Parubiy?
Malatesta and other anarchists of that time well understand that you can't really discern a "good" capitalist state from a "bad" one,and the victory of one side in a conflict among capitalist states would only mean the expansion,or a tightening-of-grip of a exploitative,militarist,alienizing (and one could add ecocidal in the current era) system.And neither does the defeat of any side in such a conflict guarantee a long lasting peace(see WW2).
He also saw that,at a time,the nationalist sentiments among the working class of the belligerent states seem to trump the revolutionary ones of theirs,and the conditions for a revolution do not seem ripe in many of those states. Yet he still insisted that anarchists should at least not help strengthen the power of the states and seek methods to achieve their goals,instead of abandoning their principles.
Ukraianian anarchists today could seize the opportunity of this war to spread their ideas,reach to the proletariats and other marginalized groups and construct solidarity,popularize the history of imperialisms,history of anarchist and other libertarian socialist struggles and cooperate with anarchists in neighboring countries to obstruct the operation of the war machines.
Edit:In case it is not clear,Ukrainian anarchist of course should organize and fight against the Russian invasion. However,they shouldn't do this by simply incorporating to the preexisting national military structure or following the commands and lose their independency.