Are you framing his attempt to correct himself as a bad thing?
There is a lot of language that was pervasive in our society which has racist, sexist, ablest, etc... origins. I grew up completely ignorant as to the provenance of these words. Truthfully, there are still a great many I am learning.
Every once in a while, I'll find myself unconsciously using one of these words. For instance, I accidentally referred to "Eskimos" when discussing something with my six year old the other day, rather than any of the proper terms.
I thought I was doing the proper thing to own my mistake, and go back to correct myself. We aren't perfect people, and expecting perfection is only asking to be let down. I think it far better to assume the best intentions of those attempting to adjust their behavior moving forward, rather than casting it as proof of some mask-dropping moment.