That’s not a bad chart, the general problem is maintaining a balance. You’re probably better off straight banning anything in the far left/right columns, because once you let a few through it swings fast.
The other problem that frequently happens is not treating both sides biased sources equally. If you make an automated message about potentially biased sources, you need to use it on all sources from each side, not equal numbers of sources. That chart has almost twice as many left leaning publishers as right leaning. This is important, because there are simply more left leaning publications (at least at the large publisher level). It doesn’t mean you have to allow NewsMax for balance, it means moderators need to be aware that most posts are going to be left leaning by numbers, which will create a feeling of favoring left sources.