Crimea belongs to Crimean Tatars. But Russia conquered them in 1783 and resettled Russians there, especially after WWII when about 230,000 native Crimeans were deported to Siberia.

In 1954, the Soviet Union reassigned Crimea from the Russian Soviet Republic to the Ukrainian one. When the Soviet Union dissolved in 1991, Russia accepted the borders and confirmed that in 1994 by signing the Budapest Memorandum.

Ergo, politically, Russia might have an equal right to Crimea as Ukraine does. Even if we agree with you that the Russian claim is the only valid one, the question is how one acts when the status sanctioned by the international laws does not fit one’s aspiration.

One can follow internationally recognized protocols, or one can act like a gangster. Now, it does not matter who has stronger rights to Crimea. Now, it matters that to preserve peace worldwide, as a matter of principle, the worldwide community needs to take Crimea from Russia and give it back to Ukraine. The best that Russia can negotiate is the internationally monitored referendum 20 years from now.

You may say that my reasoning is pointless because Russia intends to conquer the whole of Ukraine soon. That proves my point that Russia became an international gangster and it appears you are proud of it. How can I help you?