Although it is the general SE policy to not delete information that is wrong, but rather to downvote it, I don't personally see any advantage to leaving incorrect information on the site.
If an answer is blatantly providing misinformation, leaving it intact is a disservice to the Internet at large. Search engines don't preserve formatting when they present information, so depending on how it's being viewed, it could be misinterpreted even if it's at -50.
I think it would be advantageous for everyone to delete these kinds of answers. Answers that are blatantly, patently wrong do not deserve to exist on the site. Answers that do their best but just don't live up to our high quality standards are a different story.