I don't think the other people are at fault here. I think it's reasonable to assume that someone with a stereotypically black name is black, just like it's reasonable to assume that a random IT professor is male based on the fact that 90%* actually are. As long as you owe up to your error when you notice it (and e.g. apologize). It's a reasonable optimization that works out more often than not.
The problem only starts when the treatment of the person depends on the category they belong to and if that difference in treatment is not based on reason and evidence.
The problem only starts when the treatment of the person depends on the category they belong to and if that difference in treatment is not based on reason and evidence.
*example, may not be accurate