He didn't threaten them with a Navy. The current Russian navy is a shadow of its Soviet self. And it's growing smaller, not larger.
They are expanding; we are not. How much time before they surpass us?
How long will it take them to build 11 aircraft carriers, 76 guided missile destroyers, 75 nuclear submarines, and all the other ships we currently have?
If it was of paramount importance two centuries ago, how much more important now?
Don't get me wrong, I'm certainly not against a strong military. But I also don't want to spend money on ships for the sake of having ships, or advocating for a 350 ship navy when we can meet our commitments with 300. Carson was complaining our Navy was smaller than it was since World War I without considering that a couple of our destroyers could probably sink every single battleship we had in World War I. I'd like to think that there was thought involved, and not just politics.
Really does not matter what Putin threatened with; and nukes can be launched by a navy. And the primary reason for annexing Crimea is to use it as a base for the Russian Navy, frankly.
If we cannot reverse the trend of shrinking the military while our traditional and new enemies expand theirs (the goal of our fifth column in DC), then the writing is on the wall.