So, since a precedent has been set for killing innocents, it's OK to continue?
The question is, what are you going to do about it, given that one of two parties is going to control the White House: one that has blood on its hands, or another that positively glories in wading through the stuff? Which of those two do you think is relatively more persuadable on the subject?
If ending drone strikes was a driving passion in my life, one that I was willing to devote a lot of energy and time to, I would vote for the persuadable party and then spend the next four years (or however long it takes) trying to persuade them, through the hard work of organized political pressure.
I'm not that guy. But what I won't do is pretend I contribute anything whatever to the cause by casting a protest vote that may make me feel like a rad, principled dude but is no more real-world consequential than getting a tattoo that says I AM A RAD, PRINCIPLED DUDE.
If I voted for Jill Stein, my vote would simply have been sucked down a hole. I can pretty much guarantee you that right now, not a single person of power or influence, anywhere, is thinking thus: "Well, Obama beat Romney by 4 million votes, but when you add in the 400,000 votes Jill Stein got, he has an even bigger mandate to go progressive than may appear at first!"
If I voted for Obama, even in a solid red or blue state, my vote added to his popular margin, which under present circumstances did mean something. I did not want to see the media clusterfuck that would ensue if, as seemed possible, he won in the electoral but lost in the popular. When the polls all forecast a 70% vote for the Democrats, get back to me about a protest vote for the Greens.
Except even then I wouldn't do it unless their candidate gave me a convincing reason to want her in power--like competence at running a large and complicated organization, a cool hand in a crisis, the ability to deal effectively with a contentious opposition, or at least the intelligence required to edit the Harvard Law Review. Sound instincts aren't the only thing I want in a president.