Why are some animals racist?

Okay my buddy had a dog that growled at black people. The dog never growled at a person with a light complexion. But if a black Fed-Ex guy came to the door he went off like he wanted to kill they guy. If he was being walked and a black person passed by the dog growled. The other day my grandfather who has alzheimers and I went to the park to feed the ducks. We are sitting on a bench close to the pedestrian path and parking lot by the lake. There is these two geese we are feeding old bread. A white couple walk by the geese ignore them. A couple of white kids walk by the geese ignore them. Two black ladies start to walk by us and the geese. The two geese start hissing and literally chase the black ladies all the way to their car before they get in and escape.

Have you noticed behaviour like this from animals? Why are they like that. I know not all dogs are that why. Geese I don’t know about though.