I am afraid that it can be libel to republish a libelous claim. It can be damaging to Wells's reputation to call him a liar. If WP editors republish the claim, and assert that it accurately came from reliable sources, then the WP editors could be committing libel. No, it is not up to Wells to deal with everyone who calls him a liar. It is up to WP to use reliable sources and to not libel people. This particular instance is bad because it suggests that WP editors have some inside knowledege that Wells is a liar, as the article does not even reveal what the alleged lie is.