It's worth noting that the ordinary sort of implicit (e.g.) racial bias is not the same thing as being subconsciously "racist" (in the ordinary, vicious sense). We should take care to distinguish two forms of implicit bias. One might harbor some subconscious ill-will towards people of other races, which would clearly be a moral defect of character. But there is another possibility, which would involve a kind of defect or bias merely in cognition rather than in values or desires.
It's conceivable that you might have the best will in the world (even at the deepest depths of your subconscious), and yet - through some cognitive quirk - end up processing information in ways that leads to systematically biased judgments. For example, common cultural stereotypes might influence the 'schemas' that our minds use in categorizing and remembering information, and in generally making sense of the world. Stereotypes presumably also influence what "associations" are most salient or easily 'primed' in our minds when thinking about different groups (and individuals we implicitly classify as members of those groups). It isn't difficult to see how this could conceivably cause one to, say, (i) be more likely to interpret a black student's work negatively, or (ii) be less likely to think of a top female academic when selecting a keynote speaker, etc. -- without any hint of malice or ill-will coloring the explanation.
We may draw a couple of conclusions:
(1) Ordinary implicit bias, if purely 'cognitive' as described above, is best understood as merely unfortunate rather than inherently blameworthy. It's not necessarily a sign of hidden racial animus, or any kind of "racism" in the ordinary sense. So people needn't feel too defensive about it, the way they might if their good character were in question. Still, insofar as the cognitive disposition is unfortunate, and leads to people being treated unfairly, it is certainly something we should want to mitigate upon learning of it.
(2) The mere fact that ordinary implicit bias isn't blameworthy does not suffice to show that no subconscious attitudes are. We can imagine a character that really is subconsciously racist in the most deplorable sense (i.e. they harbor deep-rooted animosity towards people of other races), and such a character is surely bad in this respect -- however tolerant and egalitarian their consciously professed attitudes might be. If the subconscious malicious desire leads them to akratically (i.e. against their better judgment) perform racist acts, the person is surely blameworthy for this -- just as Huck Finn is praiseworthy for the good acts he performs, against his (dopey) "best judgment", in helping Jim escape.