It's their country, not yours.
I bet you get upset when furriners tell us our business though, don't ya?
You are completely missing the point.
If the rationale here is that Shikh’s are good guys so let them wear turbans in the UK - then you have to be okay with letting them wear their Turbans in the US while on duty. As well as other non-uniform religious items. Like Burkas. Islamic Head Wraps, etc.