The FBI is supposed to get the whole truth out. Unfortunately, there are people who want to bring politics into enforcing the law, so we need checks and balances on the entire government. That's where the media comes in. Mark Felt did do the right thing, even though it was incredibly difficult for him at the time. RIP, Mark.
(now, whether we'd have the balls to do that today, or the attention span to see it through, is another question entirely. I don't think we do, quite honestly, judging by the multiple scandals that have gone seemingly unpunished during the Bush administration.)