When someone (often an old foreigner) says something with a soft racial undertone about another race that is not meant to be derogatory but often comes out in a way that may make others slightly uncomfortable and slightly embarrassed yet sympathetic for said old person.
Often it is because of a difference in social and cultural norms that they say something softly racist.
-Urban Dictionary, "Soft Racism"
I'm sure we've all known someone who has stepped on the above-noted conversational rake without realizing it, and while it can certainly cause awkward tension in a group setting, anyone with even a little bit of emotional intelligence can finish blushing and then give the speaker a pass for their own cultural and/or age-related naïveté. For the most part it's easy to tell if the person was being deliberately hurtful or simply didn't know any better in the moment.
But there's another form of racism that is easy to miss if you're not looking for it. In fact, if you gaze into the mirror (so to speak), you may need to strain your eyes to notice it, and even then your mind may not recognize nor accept what is being seen. As for me, someone had to point it out to Yours Truly. Up until then I had been completely oblivious. What allows this racism to slip under our radars (generally) unnoticed is that it has nothing to do with any conscious intent to be derogatory towards nor marginalize a person or group based on their race, which in its own way makes it all the more insidious.
The kind of racism I'm talking about is typically expressed when you're telling a friend about an encounter you had with someone earlier that day, and you include a certain detail that has no bearing on your story. For a white person, it could be something like "I was in the express line at the grocery store and the black guy ahead of me had nine items instead of eight".
In this case, the guy's skin color was of no relevance. We are all guilty of going over the maximum number of items in the express line at least most of the time. (Personally, I usually treat the "8 Items or Less" sign as a suggestion rather than a rule.)
To test the absurdity of this paradigm, tell a similar anecdote to someone of your own race, but make the person in your story the same skin color as you and your listener. I think most of my friends or family would at least be momentarily taken aback if I said "I asked a white guy for directions."
I truly don't think any of the above is evidence of antipathy towards any one race or other races in general, and thus my intention here is not to equate it with overt racism. In fact, it wouldn't surprise me if there's a sincere and committed anti-racist or two who make this mistake with no harm or insult intended.
For myself, I used to chalk it up mental laziness. After all, skin color can be the most noticeable thing about a person. You may not recognize their identity from across the street, but you sure can tell their race. Perhaps referencing the person as "some black guy" (or "Asian guy", or "Indian guy", etc.) is a quick and dirty way to add descriptiveness to your story, and to some extent I believe this forms the basis of such a practice. However, if the person in the story is white (assuming you and your listener are also white for the sake of this example), then their skin color would lose all descriptive value.
I can't speak for races other than my own, but as a white person I can tell you that when we are describing someone to one of our own "kind", the default assumption is that the someone in question is white unless otherwise noted. By doing so, intentionally or not, we set ourselves apart from others along racial lines. While not "racism" as practiced by "hate groups" nor cause for self-flagellation, it nevertheless hints at tribalism (or what I would call "ultra-soft racism"), which to me would seem to be a precondition for hard racism in the same way that unchecked nationalism clears the way for fascism (soft or hard).
Nowadays, I make daily decision to not draw needless attention to a person's race when talking about them in the third person unless it's pertinent to the story. Sometimes it comes easy, other times it feels momentarily awkward and requires conscious effort, and then there are moments when I transgress and resolve to try harder next time.
While I wholeheartedly aspire to be an anti-racist, I also realize I have work to do. And although part of me thinks this is all a matter of making a big deal out of so very little, I wouldn't want a little thing leaving the door open for something bigger and uglier.