That’s a weasel statement. When is it enough to justify Russia invading its neighbor. First Ukraine, then America.
There is no justification.
Who said it is a justification? Russia is a guarantor of Minsk agreements. She is obliged to defend people the Nazis were planning to kill en-masse. There were multiple options for Ukraine to avoid it, but it didn’t because its sponsors wanted exactly that. They had the option to keep their country even after it has all started, but now they don’t.