I think we should leave them be, because the downvotes make it clear that it is wrong, and showing that something is wrong is useful information.

For example, if I read an answer that retells ["the airfoil myth"][1], and it has -17 downvotes, I will assume that the airfoil myth is wrong, which is correct. I actually learned something.

If the answer was deleted, then maybe the idea of the airfoil myth may creep into my mind some day from other less reputable sources.

**A biology point of view:** Being exposed to harmful answers in a controlled environment, where they are downvoted, shows you they are wrong and thus gives you an "immunity" to them, that remains after you leave this site. Very much like a vaccine.

**A geometry point of view:** *Ideally*, positive votes show how correct an answer is. Then, negative votes show how incorrect it is. If an answer is a 2-D vector pointing towards an idea, then a negative count inverts the direction, pointing *away* from a wrong idea.

**A logic point of view**: [The Raven paradox][2]

**An engineering point of view:** Squeezing some right knowledge even from wrong answers is *efficient* at the least. Deleted answers give nothing at all. Plus moderators don't have to be deleting extra stuff. Unless storage space becomes crucial, then yeah, delete.

Edit: the original answer used "chocolate electrons" as an example, hence the comments.


  [1]: http://warp.povusers.org/grrr/airfoilmyth.html
  [2]: https://en.wikipedia.org/wiki/Raven_paradox