In the 1950s places where others who were different were excluded or forced to take a back seat were extremely common all over the country. Everything from colleges, to country clubs, to motels, to public conveyances, to theaters were segregated by race, religion, gender, and class. A great portion of the population were publicly treated like pieces of shit. The Washington Redskins didn't even sign a single black player until 1962, and that is no comparison to Kaepernick's kneeling. He couldn't kneel if he couldn't play.

Where are you going where people aren't polite to you or others now? Most people today are polite to everyone in public, not just people who are like them.