Displaying a Confederate flag can also be an “expression of speech”
Or a decal . . . or a “white nationalist” website You get the message.
And yeah, go ask Berkeley about “free speech” In fact, almost any college or U. Ask Mizzou about the effects of pandering and denial of speech or association.
It's moderately amusing to see the left's shifting rhetoric from week to week. Had the big controversy concerned a player who was waving around a Confederate flag, they'd all be saying something very different.
I just read a self-unaware comment on another site. The poster was astonished at "conservatives" who defend the display of the Confederate flag as "free speech" but disapprove of the kneeling. Well, poster, if the two things really are functionally equivalent, then your simplistic argument would go the other way too, and those who defend the kneeling as free speech shouldn't be disapproving of other expressions thereof.