Are animals racist?

I've actually seen research on this, and the short answer is yes, kind of.

The long answer is a bit more complicated. Dogs obviously don't have notions of racial stereotypes, but they do live with people who have them. We know even minute changes in the demeanor of their human can cause dogs to mirror their emotions, so if their handler has a fear/distrust/etc response, even subconsciously, the dog may pick up on those tiny cues and associate that emotional state with the trigger. There's a ton of research to show that nearly everyone shows these subconscious prejudices to some degree.

Gaps in socialization can also create racial prejudice in dogs. If a dog isn't adequately socialized with people of different races, they may show signs of fear or aggression toward people of color later, just like they might with kids or people with beards or cats if they don't have frequent positive exposure during development.

Finally, even when these other variations in experience are controlled for, many dogs still seem to show a preference for lighter skin tones (in people and in other dogs). The hypothesis is that dogs have a harder time recognizing body language (and especially facial) cues on darker skin tones/fur color. Dogs don't have fantastic eye sight, so facial cues in low contrast may be harder for them to recognize, and as a result they are more wary of or even aggressive toward people/dogs they find difficult to read.

I would say it depends on the dog and their experiences. I acquired an 8 week old Rotty puppy, her previous owner was a black family. From the first day I had her she did not like any black person. I took her to petco when she was six months old when a black police officer attempted to get in line behind us...it didn't go well and the officer actually drew her weapon. (No shots fired) At 12 weeks she went after a black kid in the Wendy's drive through window. So my answer, is not that they are necessarily racist, but bad experiences can affect their behavior.

It's based off of socialization. One of my dogs was abused my a black male soldier prior to our adopting her, we know this because she panics and growls at black males in their uniforms, but is fine in general with most other black males, and female soldiers.

I'd answer no. However, each person has a scent about them based on diet, medical status, hygiene and many other factors. Due to their amazing sense of smell, they may be more drawn to or repelled by certain people. From Petmd.com: The canine nose is thought to be between 10,000 and 100,000 times more sensitive than the human nose. In addition, a greater portion of their brain is dedicated to interpreting this massive amount of data.

However, I also agree with the commenters that previous experience history definitely can impact future behavior, as can handler reactions/behavior, and socialization.