the entire Bill of Rights only applies to the government. At your place of employment, you have no right to free speech, no right to bear arms, and no right to reasonable searches or to remain silent. Your employer can infringe on any of these rights and terminate you if you don't comply.
Well, the Bill of Rights applies to the government as binding them as guarantor, doesn't it? I'm not a lawyer, but I believe there must be remnants of civil rights remaining at a workplace. I guess that means I have my rights, but my employer can always fire me. I can lawfully carry, I can't force my employer to do a happy dance.