What is cherry-picked about them? There aren't very many real American attempts to begin with, of course a discussion will include Sirhan or Oswald. One of the two had military experience, yes, but nothing especially relevant and long-gun experience is easy to pick up (heck, I probably shoot as well as he did).

Further, I would think the recent example of Jared Loughner demonstrates that you don't have to have to be very good to be a good assassin - by sheer bad luck he may not have actually killed Giffords but he did manage to pretty much kill her career inasmuch as she can barely vote and I doubt she'll ever do anything of political significance again, I would not be surprised if she doesn't even run for re-election.

(And what if you are serious about it and plan things out? Then you'll be an Anders Breivik!)

Again. The fraction of assassins that had significant political effects is much much larger than the fraction of people working through conventional channels having significant political effects. I don't see how one can dispute this, and would appreciate people being explicit about how they think the fractions are not hugely different or even in favor of conventional channels. (Once you have power, engineering it to predictably accomplish what you want to accomplish is detail-work.)