Mercedes Benz appear to be condoning this if not participating, by painting their racing cars black (they've been silver for 100+ years) and having the team in black overalls. The T shirt stunt by their lead driver yesterday shows how easily these things can get out of hand and they may well see sales suffer, particularly in North America.
As for resolution of the knee fad, yesterday gave the FIA the perfect excuse to take the lead and stop it in their sport with only a few people involved. They can threaten to withdraw the racing licences from any drivers or teams that bring politics of any shade into the sport - as they would with safety, health and other issues.