I am looking at forced patriotism quite objectively. You on the other hand are reacting to peaceful protest with an extreme emotional over-response.
Football players taking a knee are not protesting the flag, America, the military or baseball, hot dogs and apple freaking pie. They are protesting racial injustice, period.
The reason the First Amendment included the right to protest, was so that people could protest against the government. The 1A basically forbids the US Federal Govt from stopping people protesting them. This was done so that politics could be freely spoken about, so that people could discuss the issues that need to be discussed, instead of the govt being able to prevent people from talking about things the govt doesn't want them talking about.
The flag, the anthem etc represent the US government. They're there to be protested.