With all due respect, but the US did the same thing with California, AZ, NM, etc...which belonged to Mexico.They illegally took them by force.
The peace was reached thanks to the Treaty of Guadalupe-Hidalgo, only because Mexico was too weak to fight back, in 1848.
We need to understand, that even if we disapprove of the modalities, those are regions where Russian-speaking populations live, and if that's the price to pay to get peace and concord, it's a very small price. It needs to be paid.