Business doesn't play by the same rules as the government. The long and short of it is the not standing for the anthem is costing the NFL money. If they weren't losing money/viewers or having trouble with sponsors they wouldn't care one way or the other.
I was thinking about this earlier, after reading a football player making a statement about making him stand squashes his first amendment rights. No it doesn't. He's still free to kneel if he wants - nobody is going to arrest him and cart him off to jail. Will his employer punish him for going against policy and ceeating more turmoil that could cost them money? Possibly. Probably.
Is it forced patriotism, or good business? I don't know. Certain actions are causing the business distress. Therefore, it is in the business' (and the employees of said business) best interest to bring it to a halt and start making money again before the damage done is more costly/difficult to recover from.
Another thought on forced patriotism... my generation and prior grew up with it. We were made to stand and say the pledge of allegiance in school. We were made to stand for the national anthem. If we didn't, there weren't "safe spaces" we could go to. We weren't considered to be "expressing ourselves". We were considered deviant, and we got in trouble - in some cases we got our asses beat if we didn't do as we were told.
Different world, different times. Shit, I'm sounding like an old fart! GET OFF MY LAWN YOU DAMN KIDS!!