first off I think this is a good idea, because the guns most likely to be stored in the cars are guns people conceal and carry. Conceal and carry permit holders are in general law abiding citizens.
In general, permit-holders were model law-abiders. Even off-duty police officers in Florida were convicted of violent crimes at a higher rate than permit-holders.
Secondly, the law does nothing to prevent work place violence. The people who are going to shoot other people at work do not care about some law where their employer can fire them from their job if they bring a gun to work. Those people who are going to come into a work place shooting are crazy and know they are going to die anyways. The people of okla. Should at least get the chance to shoot back.
Also, if you company prohibits you from bring a gun to work, them they would also have the responsibility of protecting you. Which the police departments do not even hold their sevles to such a high standard.