I don't understand what the underlying suggestion is (if there is any). PM isn't a book, it's a community: you can give to the community even posting wrong answers. I may agreed that deliberately posting wrong answers would be bad, but I haven't seen much of this here.

Stopping the red light should result in wrong answers being cut out? I agree with revdiablo, and I prefer to see a correction post by some other guy than nothing at all: it gives yet another point of view, helps to dissipate bad practices by making them stand clear to all and preserves speech freedom.