The wearing of the cross would likely come under infection control rules, in which case it is certainly not ridiculous. Medics on ward rounds can't wear ties either and must roll their sleeves up to the elbow. Ridiculous eh? Hospitals trying to stem the spread of superbugs, I ask you!
Perhaps it would help stem the spread of superbugs if hospitals went down the old road of not allowing more than two or three visitors per patient, made it a firm rule that said visitors should sit on the chairs provided rather than on the bed, and brought back the former visiting hour rules. I had the misfortune to be in hospital 12 years ago where visitors could come in between 2 and 8 pm and some patients had their whole family, kids included, sitting beside and on their beds, eating food and effectively turning it into a day's outing. So please don't tell me that that doesn't increase the chances of patients catching superbugs. Also it's extremely annoying for other patients to have to put up with this, particularly as the visitors were allowed to remain well beyond 8pm.
A company has a right to impose uniform rules. You and the Christians wearing the crosses may not like it, but it's not evidence of the dreaded 'PC' brigade trying to spoil anyone's fun.
I have no objection to uniform rules or a dress code, but, and I'm what you might call a non-practising Christian, I certainly don't see why the wearing of a cross should be one of them.