So for example, does news corp or the wallstreet journal ALWAYS lie? Obviously not.
No one said that they always lied.
No one even said that they lied, only that they were not credible.
For instance, if I said that the advice of financial advisers was not credible because it was no better than a bunch of monkeys randomly throwing darts at a list of mutual funds. It wouldn't necessarily mean that those financial advisers purposefully lied with their advice.
For instance, it could mean that they have a bias of some kind, known or unknown. It could mean that they prefer to choose funds that sound cool and trendy, so that themselves sound cool and trendy when speaking to clients. It could mean that the person who hired them or the person who owned their company had a bias of their own and selected financial advisers that followed the same financial schools of thoughts that he did. It could mean a number of other things too.