To very many Americans (who are sincerely patriotic and have fought for their country), using free speech to disrespect the flag is tantamount to using free speech to yell FIRE in a movie theatre.
Not everyone will agree with this, but it is not hard to understand their point of view and CK might have considered respecting their feelings on this matter. As I said earlier, there are other ways he could have expressed his feelings and respected the feelings of other Americans at the same time. It was a poor choice on his part. Not necessarily wrong, but definitely not wise.
I question how many people would really stop watching the NFL due to Colin's actions.
Football is religion in the US.... high school coaches are paid positions, college is big business and NFL is massive (just look at Super Bowl ad time costs).
Hard drug users, steroid users, animal abusers, wife/child abusers, gun charges, DUIs, bribe takers has not slowed down the industry.
Anyone here watch "second chance U" on Netflix..... it is a D2 school that is known for taking D1 guys who have gotten into trouble.
It is well documented that teams will take "risks" on players who would be "distractions"
Heck Marshawn Lynch took a knee while in a Raiders uniform..... when asked about it he just dodged the question. And he has sat out for at least a season and not getting younger. In my opinion a guy like that is way worse than CK..... checkered past, thuggish looks and terse interviews..... I personally like him but if the flag wavers have a problem with CK surely ML would be equally objectionable.