I wouldn't consider them that terribly biased personally; as their livelihood (Money) is put into shorting whatever company is being reported on (Mouth). Literally they put their money where their mouth is...and if they make a horrible mistake in reading a company going under and doing really shady things; they're going to basically go out themselves pretty quickly and lose a lot of credibility in the process.
Is it maybe a little scummy? Yes. But as they're calling out scumbags anyways; it looks more like a legitimate application of "taking a scammer to know a scammer". It's better that they're legitimately profiting from calling out companies that are cheating everyone and reporting on it to benefit the public in the process.