That's an over simplication. I don't quite see the problem with shooting condemned people for fun (provided they experience more or less the same amount of suffering).
But I would point out that your example is loaded since I can't seem to see a senario where extermination of the enemies of the United States would be done for fun. The only reason we kill those people is because they are enemies. If they weren't we won't kill them. Whether we enjoy killing them is a different matter.
The crux of my argument is that it doesn't matter if you enjoyed killing ant colonies/terrorists. You still achieved the same result (dead ants/terrorists).
You believe it is morally reprehensible to have enjoyed killing ants/terrorists. I disagree. Does it matter what the executioner feels when he decapitates his subjects?
I won't advocate the destruction of ant colonies in forests because for ecological reasons, not because of individual ant suffering.
To me there are ecological and moral reasons why you should not destroy ant colonies. I am aware that not everybody agrees.
Regarding the drone strikes: whether videos of the strikes are also used for entertainment is irrelevant here, as long as it is not part of the motivation behind performing the strikes.
I don't think motivations factor into it at all. A death is a death.
I don't know what you are getting at here. Are you seriously suggesting that shooting people for fun is morally equivalent to shooting them for a good reason?