You can call millitant expansion imperialism, but Marxists don't have a problem with the word, but the actual, material process of what we call imperialism. Millitant expansion can be done for progressive reasons, like when the Statesian north liberated the slaves in the Statesian south. The actual economic form of international extraction as a special, necessary part of late-stage capitalism is what Marxists are trying to dismantle, due to it being the biggest obstacle to global socialism.

As for Ukrainians supporting their government, you're half-right. Western Ukrainians tend to support their government, while those in the Donbass seceded from it after the Euromaidan coup, and voted to join the Russian Federation.

Overall, we aren't arguing about words, but processes. If you insist on calling millitant expansion "imperialism," then we have to agree to what we call the Marxist understanding of late-stage capitalist imperialism as a special term as well, so that we don't get mixed up on terms.