I found out that my prejudices were in error when I was in a jury that included a fellow whose heritage and name indicated he was from one of those MiddleEastern countries we get terrorists from. (This was before 9/11)
I had assumed that he was Muslim. It turned out, that when we jurists went to meals, we found out personal stuff about one another as we were NOT allowed to discuss the case before the trail was over and we'd received ALL the evidence that was going to be presented. (What a concept!!!)
Turns out, this fellow was JEWISH!
I had, with my broad brush, had tarred EVERYONE from a certain area with the same characteristics.
The trial was quite a teaching moment for me.
Don’t toss everything aside over one error of judgment.
Your error was only that of misidentifying the ethnicity of the person.
Your so call prejudices, which are really post-judicial (judgments based on experience, knowledge, and wisdom) were correct.