NO ONE herein is asking for a federal law to be enacted to make kneeling for the anthem illegal (instead of just vacuous and stupid). You make the same mistake about what are "... your first amendment rights" that many others do. The Constitution may protect your right to say stupid things, dangerous to your financial well-being, from government interference; IT DOES NOT protect you from the consequences of the choices you make
I think we can take that too far. When society gets so polarized that they mob-shame everyone who doens't conform, then we have a defacto tyranny. Rather than mob-shaming, I'd rather leave people to their own morals and I'll worry about mine.