Most countries are made in a way to not allow parts of their territory to secede, even if they "want to do it". Just look what happens in Spain with Catalonia, what would probably happen in Scotland, Texas or California. This is not fascist.
But, you are ignoring the fact that Crimea did not decide to secede but that Russian soldiers (without insignia) became little green men, they forced Ukrainian army to surrender their weapons and leave Crimea. After that Russia organized "a referendum" where Crimea voted to join.
How well these referendums work we can see in Kherson.