I am sure that many journalists realised that this was a joke, but chose to report it 'straight'. Journalists - and their employers - love controversy.
Yes, journalists should check their sources, but let's save the outrage when they don't for issues that really matter. Every day in the media we get uncritical reporting, often near-verbatim, of government propaganda and press releases from politically affiliated think tanks and drug companies and other commercial enterprises. That's what we should be objecting to, not traditional Xmas spoofs.