Sallow
The Big Bad Wolf.
To do what must be done & chop it off? This is an easy opportunity that Putin himself has served up to Obama. Putin has made Obama look foolish at every turn up to this point. This is Obama's chance to oust Putin from the world stage, does he have what it takes to do it?
First off, there is no "chopping" off of the hand. Diplomacy and Geopolitics is a chess game.
The whole world knows that Russian operatives shot down that plane. The US even claims to have actual footage of the launcher being driven back across the Russian border. Putin still has 10's of thousands of troops directly on the border. Putin could immediately allow investigators onto the crash scene if he wasn't trying to cover it up.
Balls in your court Obama
And playing the "ball" right includes deliberate and careful strategy.
Even when it seems everything is in your favor? Overplaying it generally leads to bad outcomes.