Wikipedia is not as good as you might think. Things written on Wikipedia are copied “verbatim” by other sites. By the time somebody checks the wikipedia story, he finds the verbatim copies and sees them as confirmation of the wikipedia story. And so the story stays on Wikipedia, spreading wrong ideas to schools, teachers, and you and I.
Spreading wrong information on the internet can have very big consequences, and John Seigenthaler knows this by personal experience.