How can people have such differing views about what the Constitution is all about?

Some people get all bent out of shape when they see something they perceive as “disrespecting the country,” such as taking a knee during the anthem, and talk like it should be a punishable offense, where as others, like myself, recognize that it is a Constitutional right to free speech and peaceful protest, and they are protected under the law.
How can there be such opposing views?