Crimea was part of the Ottoman Empire for 3 centuries and a part of the Golden Horde for 2 centuries before that. What's your point? Just because some state controlled the territory in the past doesn't mean it belongs to it in the XXI century. This world came up with the international law and rules for a reason.

The point is that it’s not historically Ukrainian and that given its history Russia has more claim in it than the other claimant. And given its strategic importance, I don’t see them giving up that claim.

It’s akin to China asserting a claim on Guam. We will not let that happen.

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.