The Commander-in-Chief is accountable for all actions of his troops.
If there had been a single drone strike killing 'terrorists' and/or innocent civilians and Obama had halted this form of political assassination after a single incident, then you would have an argument. The fact that hundreds of people have been killed by drones, some of them innocent bystanders, during numerous drone missions and often on direct orders from the White House, Pentagon and CIA, directly splashes blood all over Obama's own hands. Not to mention all American citizens culpability. The fact we are not demanding an end to these atrocities means we, the people of this country, are guilty also. It's going to be hard to get anyone to listen to us once the drones are directed at ourselves. As has been threatened.
Would the drone operator's have sent the drones to assassinate without receiving orders to do so? The operators are probably not allowed to use the drones for personal errands. They, like the drones, follow orders.