In light of the current situation, Ukraine's desire to join NATO is clearly justified. Ukraine was concerned about Russian aggression, especially after the Crimea, and wanted protection. NATO membership became a shared goal for the majority of Ukrainians after Russia's military occupation of Crimea. Who is Putin to deny them that right?
Regardless of how you spin it, aggression against a sovereign state with a legally elected government can never be justified. No matter what the issue, Ukraine's sovereignty and independence must be respected by all powers. Putin is a war criminal and it is time for Western countries to stand up to this aggression.
Certainly, invading a country isn't justifiable by any means, while Putin's threats are definitely real and concerning. There needs to be a stop to his madness, but I don't see it happening.