It's their choice and their right.
However the only reason they could have for not wearing them as that they don't support the campaign. Whether that be for religious reasons, well it may be, but the conclusion is the same.
No, thats not right. If someone chooses not to do something that everyone else is doing I don't think automatically think they must not agree. Some people don't like to be told they have to do something. It's like the ice bucket challenge. Same thing. If you choose not to do it people said 'oh don't you agree with it, it's for charity, you're just mean, it's really fun, yada yada yada'.

