Then work for someone else. No one is forcing you to work for a given employer.
No one is forcing you to do business in a country that respects employees RKBA's.
The point is that employer is, in indulging its bigotry, jeopardizing my safety and the public safety in general. By attempting to create a so-called "gun free" zone in its parking lot it is actually creating a criminal's playground in that parking lot with the attendant risk of increased rapes, robberies, and murders. Every state that's adopted shall issue CCW has seen a substantial decline in violent crime, and undeniable fact. When an irresponsible employer recklessly indulges its bigotry against guns, it's doing something tantamount to blocking fire exits.