With all the rapid-fire controversy surrounding the NFL and the national anthem protests, people might lose sight of why protesting the national anthem is so upsetting to Americans in the first place.

Today, on the anniversary of the D-Day invasion of Normandy during World War II, veteran Navy Seal and New York Times bestselling author Robert J. O'Neill reminded everyone "why we don't like kneeling."

The sacrifice of generations of American soldiers of all colors, faiths, and national heritage who died to defend their families and their country is profaned by protesting the national anthem.

And that's why people get upset.