Are we talking about the SAME armed forces?
This guy is a Sikh, serving in a BRITISH (or CANADIAN) unit. We’re not speaking of the US military. As far as I know, they DON’T allow turbans to be worn in any of OUR armed forces, and also as far as I know, there aren’t any plans to change that.
It’s the same principle.
If you think it’s okay for a turban at Buckingham Palace then it’s okay for a Turban at the Tomb of the Unknown Soldier.