I used to think like you - Wheres the evidence? They don't have a swastika tatooed on their face and didn't call you a slur, how can you know they were racist?

But here's the thing, not all racism is overt. There's more subtle ways it plays out too - patterns of behavior and the like.

When I was in my early 20s I worked at a bar owned by a black man, and I'm a white man. His role was basically manager, and I was basically assistant manager - and in the small bar world that meant we both were jacks of all trades. We did janitorial work and bookeeping and serving and really all the jobs of a bar. Depending on what each of us was doing that day, we could be dressed down and dirty, or dressed up and looking like a million bucks. Some days i would look basically homeless and he would look like a well of guy, and some days it would be the opposite. Some days we'd both look the same in that respect.

Over time I noticed a pattern - independent of what task we were doing or how we were dressed, I would be approached by people wanting to do business first. Distributors, musical acts, promoters, maintenance workers, and even cops would approach me for manager intereactions more often than they would approach the owner. No matter what the outward appearances were, I was the first person approached 2/3-3/4 of the time.

Any one of those instances could easily be rationalized away - Oh the well dressed guy was approached as manager, or they didn't want to bother the manager to begin with so they approached the worker first, or they approached who they saw first, or ..., or...

But after a couple years of this, there really was only one pattern that was consistent: they approached the white guy first more often than anything else. Most of the people who came in to do business never said or did anything overtly racist. I suspect most of them wouldn't consider themselves racist and they likely have black friends and think the concept of racism is irrational. Yet the fact remains - in a 50-50 situation, the white guy was selected as likely to be the boss a lot more than 50% of the time.

Yes this wasn't real science and theres a multi-variable statistical analysis that would be needed and all that jazz, but it was enough for me to become aware of the pattern - as i said any one of those situations can be rationalized away, but the fact that each situation needed a different rationalization and the racial bias explanation was much more consistent throughout was enough for me to believe that maybe there's more to racism than wearing a hood.

Relating this back to the cop story above - sure you can rationalize this one incident however you want. But over time, pay attention - you'll find disproportionately more stories about such cases of 'mistaken identity' being applied to minorities than white folks in the US. This is what people are talking about with institutional racism or societal racism, the fact that it's assumed that a person is a criminal or a boss or whatever based on thier race (not the race of the assumer, that in and of itself is a racist notion - "oh the black cop assumed the black person was a criminal disproves racism because all black people are a single group and represent a single viewpoint").

Try it on yourself - walk into a high end or middle class establishment where most of the people are a different race than you and pay attention to your comfort level. Compare it to your comfort level in a similar establishment where most of the people are the same race. When you meet a person, pay attention to how surprised you are that they have some role, or some power level and if that matches what you expected first looking at them. Racial bias comes in part from how our society is set up wrt race - you probably aren't racist, but I bet you have racial biases anyway. I do - most people do, a lot of it is taught long before any experiences. The best we can do is acknowledge to ourselves the times we made stupid assumptions that had no merit, and update our priors - this can be upsetting sometimes, I know I would love to say I got where I am on my own, but my observed reality is: there's a lot of racism in the world, and I'm in the "easy mode" group.