One of the biggest invisible biases is thinking you've managed to free yourself of invisible biases.
I'm reminded of the inevitable "I'm not biased, but I'm going to complain about this because I think it's an attack on me" that comes up whenever anyone on the internet mentions that institutional racism exists.
It's like trying to convince someone that you're not crazy when they already think you are. It doesn't mater, anything you say or do just reinforces their belief.
We all hold biases and prejudices for just about everything from concepts, ideas, products, institutions, and especially one another based on their history, race, creed, social status, clothing, voice, stature, hometown, manner of speaking, educational background, career field, job title, wealth, attractiveness, political beliefs, the list goes could go on for pages. But trying to equate these kinds of biases to being *-ist in any meaningful sense is missing the forest for the trees.