The problem is that there is lots of research indicating that while many people will swear up and down that this is what they do, in many cases it subconsciously isn't the case.

Had you asked me two years ago or so I would have absolutely sworn that I was no way biased with regards to gender, but about a year and a half ago I started to seriously introspect on these issues, specifically trying to focus on my subconscious actions and running through past interactions, and now I honestly don't feel confident claiming that anymore. I obviously never actively discriminate and try to be aware of my action, but the subconscious is a hard thing to control.