Easy cop-out to avoid flak for mistakes or being plain wrong, by one of the most popular shows on the internet at the moment, which prides itself on being so much smarter than everything it mocks. I'm getting pretty turned off from Oliver, tbh. Why not just have the balls to 'fess on your own mistakes and fallibility, instead of backing off saying it's all for jokes. It's more than that, he tries to send a serious message in each episode, so that's bs.
The show makes fun of its "research" often, citing that they've been hard at work since "this morning" etc. They're pretty clear that they don't dig too deep. This in and of itself is part of the joke. His little show turns up facts and information that mainstream journalism either willfully disregards or just plain misses. That's part of the satire. It's not journalism, but by its nature it's a giant fuck-you to journalism, in the same way that the daily show and Colbert are.