So, journalists get a pass when they 'investigate' someone, but the people they're investigating can't do a 'counter-investigation'? Are journalists some kind of special beings?
Journalists are not special beings, but it is typically presumed that they report in good faith, and without ulterior motives. I know that isn't always true, but it's true often enough that I think the burden of proof would be on the people being investigated to prove that the journalist's intent was malicious.