It has been my experience, at least within the U.S.A., that the phrase, "shut-up" was tatamount to "FUCK-YOU"

In the past, there has been Unbelievable Offense, Ubridge (sic), taken by the offended party.

However, they HAVE deserved the "disciplinary action."

"shut up" is not Fuck You!

But I have been more than happy...that they have interpeted "it"...that way.