As Bill Hicks said (regarding people being offended by individuals burning the flag), the soldiers didn't die for the flag, they died for what the flag represents... which is the right to burn the flag.
Honestly, I'm always shocked that someone would be so irate at the idea of a player kneeling during the anthem. Imagine if a member of your family was killed and you were refused justice, everyone refused to even listen to you. Then a player hears about it and kneels during the anthem to draw attention to your story. Would you tell them "thanks but no thanks"?