You are correct about the symbolic nature of the US flag here in the United States. But this is not about the flag, this is about a dress code of a company. If the company dress code says no lapel pins, it means just that - no lapel pins.
I cannot for the life of me understand why there is a concern or apprehension about this offending someone. If someone from another country is checking into the hotel and they are upset about seeing OUR flag on the front desk clerks jacket, THEN TOO FNG BAD ! Go about your business in this country and then LEAVE - return to the comfort of your own flag.