In GitHub: how do we block a developer's racist avatar from being displayed?

Background: When looking a commit chain in github, the committing developer's avatar is displayed. This is a nice feature especially in these remote days.

A former employee has a blackface image as their avatar.

We tried contacting github and we were told how to block the developer. Clearly, an unhelpful answer.

Does anyone here know how to block just former employees from having their avatar displayed?