There has never been a shortage of criticism of certain admin actions. A high proportion of this has always been mud-slinging by those rightly the target of admin sanctions.
The issue of 'bias' is better phrased another way. Do admins apply admin powers in attempts to control article content, in a way that is negative from the point of view of compliance with fundamental policies on content? It turns out that it is much harder to make a good case of this kind, than to make general accusations on 'bias'.
It is not. A user named Saladin1970 was recently indefinitely banned by administrators because his political views was diametrically opposite to theirs. There was absolutely no reason for that ban, and had Saladin1970's political views been better aligned with theirs, he wouldn't have been blocked at all. Since virtually all his edits were reverted solely because they were made by a blocked user, it should be painstakingly clear that (some) admins apply admin powers in attempts to control article content and that that is negative for Wikipedia.
And it won't change, because despite the probably hundreds of policies wikipedian-en has, not a single one of them says that when an admin fucks up that bad, s/he shouldn't be an admin. So while Saladin1970 is stuck with some weird arbitration thing with Fred Bauder, the admins can continue their free roll. Saladin1970 is far from the only case, he just happened to be particularly persistent and polite when complaining in this list.