As concerns your American Indian question, suppose you own a bakery and they want a cake depicting Custer's slaughter at the Little Big Horn which they need for a celebration of Custer's death.
The bakery in question didn't bother to find out what was on the cake before refusing service.
I don't buy that businesses providing materials are participating in the ceremony, either. There is a qualitative difference between someone singing in the choir and someone who won't even be there.