The counter-argument is that, often, it's more effective to coopt your opponent rather than to fight him. I reckon that giving them NS2 would have avoided this war - at worst they'd have taken just the Donbass like they took Crimea.
...Keep your enemies closer aside, one does not hop into bed with a hostile power and just expect things to go well. They will not hesitate to pull out of the arrangement when it hurts the most. In fact, one can practically count on it in most cases.
