Notwithstanding any other provision of law, the operation of machine shops and rubber molding and plastic injection molding facilities shall be exempt from the provisions of this chapter. No person shall be required to work on Sunday who is conscientiously opposed to Sunday work. If any person refuses to work on Sunday because of conscientious or physical objections, he shall not jeopardize his seniority rights by such refusal or be discriminated against in any manner. Sunday work shall be compensated at a rate no less than that required by the Fair Labor Standards Act.