Meffi-Investigative journalism is not "biased;" it is goal directed, the goal being the public exposure of some wrongdoing of interest to the public, or in the public interest.
If there is only one side to a story, and that side is negative, there is no requirement to attempt balance. The only bias that would be objectionable would be omitting facts that were exculpatory, i.e., selective reporting, or refusing to admit to errors once they were pointed out.
Was the Watergate reporting "biased?"