Should employers also be forced to provide freezers for people who come to work with an ice cream cone, which they are not allowed to take into company premises?
Employees don't have a fundamental right to bear ice cream cones, and the lack of an ice cream cone during travel to and from work isn't life threatening.
The 2nd, or any other, amendment does not trump private property rights. It's a restriction against government power. I would be fired on the spot if I would start to publicly advocate for boycotts against my company (i.e., the 1st amendment does not give me the "right" to not to suffer in my private contractual arrangements due to my public statements).
Neither do employees have a fundamental right to stay employed against their employer's wishes.