You can't call it money. You can't even call it a coin. You can buy, sell, and trade "rounds" of silver and lots of people do. It's when you try to pass it off as an official currency that you have a problem. Liberty Dollar had a marketing plan that involved convincing a lot of ignorant people that it was an official currency. The markup on it was obscene. Libertarians were into it for making a statement about alternate currencies but most people are not going to value a silver round at the face value of a liberty dollar unless you convince them that "suggested retail value" is somehow an official thing and that people are required to accept it like they are U.S. currency.