On the contrary, both Ukraine and Turkey could make a more legitimate historical claim than Russia, and independence is even stronger. Russia does not have any legitimate claim to Crimea. China and the US are peers in terms of national power. Ukraine is a former vassal state of Russia that is much poorer and weaker, and Russia is also trying to annex the eastern portion.

Where the heck do people get off on justifying imperialist annexation of smaller, weaker countries by an aggressor?

You are correct about strategic importance (which is still not tolerable). But it is not correct to justify this annexation by any historical reasons.

That's like saying Ukraine has claims in Kuban, because it was historically Ukrainian.