Well, I can't see annexing a part of your neighbor as a defensive strategy. As for the "Western threat" idea, do you really believe that the west has any interest in invading Russia? The only invasion I see is the invasion of ideas, which must be terrifying to him. As rebuttal to his critics he promptly has people put in prison because they express dissent. He has quite the propaganda machine (and I'm not talking about a goose with a neck tie) to keep his message out there mostly unopposed.
The West don't want to invade Russia or Ukraine. We just want Russia to calm down and stop invading its neighbors. Accept international borders and the sovereignty of other nations. Use its leverage in the region to pull for equality, acceptance of differing ideas and most of all for peace.
Does that mean Russia will have to deal with change in ideas and a shift away from the old soviet paradigm? Yes, but Russians (especially the Russian youth) will be the ones driving change with picket signs and ballot boxes, not foreign tanks.