Russia believes it is entitled to respect from the rest of Europe, leadership of all Slavs wherever they may be, and obesiance from any "lesser" nation (i.e., anyone except China) with whom they share a border. They just believe that is their due, and are offended if anyone refuses to accede to that. NATO undermines all of that, which is why they don't want it to expand. Not because they actually believe NATO would ever invade.
F*ck 'em I say. You are only entitled to whatever respect others choose to give you, and other countries should be free to thumb their noses at you. It apparently is going to take more Russian dead in Ukraine for them to learn that lesson.