Unconscious bias is, to my mind, not that useful to tag as "racism", just as it isn't useful to tag it as "sexism", "homophobia", etc. It may be the same, it may not, but it 'feels' like a very different animal to me an, crucially, I think the language risks alienating people and giving them a drive/reason/excuse not to engage in changing. I have no idea what we should call it, and I'm all in favour of acknowledging and addressing it, I just think there's a major 'PR' problem here.
There is a long, righteous, and on-going battle against explicit discrimination, violence, and oppression. An awful lot of people are, I think, actively repulsed by the idea of being called a racist because they associate it with (still very real) behaviours to which they are genuinely utterly opposed. To lump unconscious bias in under the same term risks, to my mind, driving people away form a conversation that they really need to be part of.
Unlike explicit bias, unconscious bias is really hard to legislate against - it has to be resolved by individuals engaging with the debate and becoming more aware. Whereas you could argue that you don't need to change the minds of the KKK to prevent lynchings, you just need an effective law enforcement, you really can't say the same for unconscious bias: it has to be a'hearts and minds'' battle. And so anything that alienates people from engaging with it is pretty bad.
I also don't think it necessarily helps to 'dilute' the word "racism" I don't want someone who is clearly branded a racist to get the benefit of the doubt: "Oh, he's just one of those unconscious bias racists, not the bad kind" - fuck that noise. And, yes, it's fair to say I don't particularly want to be a racist myself, but the evidence seems to suggest that on some level I quite well might be unconsciously biased against some types of people. If the language is alienating me then, in all modesty, I think there's going to be a pretty big problem when it hits the high street.
Obviously, as with sexism, homophobia, etc, there's a lot more to the issue than just the strand that I'm pulling at. But precisely because it runs across a wide range of discourses, I think it's maybe important to consider.