If you were to kill an idea, how would you do it?

Many comments on another question were to the effect that “you can’t kill an idea,” since an idea isn’t mortal biology. So I’ve been trying to figure out what “killing” ideas, these tenacious little creatures, would even mean… I realized I wasn’t sure. Would an idea be dead if everyone forgets it; or if it becomes marginalized; or if it becomes replaced by a newer, shinier idea; or if it is condemned in the public eye; etc.? Each definition seems to suggest a different strategy of attack, and a different problem… But let’s imagine it’s possible:

I turn to you, fellow jellies. I offer you any and all resources available in the world. Everything is at your disposal, limited only by your ingenuity. How would you go about killing an idea?

… This seems, also, to depend heavily on what the idea is, and how rooted it is in people’s minds. So go ahead and define what idea you are attacking, too, if that helps.