Any threat, express or implied, made to a retailer by any person, or any agent of any such person, who is engaged in the business of financing the purchase or sale of motor vehicles or of buying conditional sales contracts, chattel mortgages or leases on motor vehicles in this State and is affiliated with or controlled by a manufacturer that such manufacturer will terminate his contract with or cease to sell motor vehicles to such retailer unless such retailer finances the purchase or sale of motor vehicles only with or through a designated person or class of persons or sells and assigns the conditional sales contracts, chattel mortgages or leases arising from his retail sale of motor vehicles only to such person so engaged in financing the purchase or sale of motor vehicles or in buying conditional sales contracts, chattel mortgages or leases on motor vehicles, shall be presumed to be made at the direction of and with the authority of such manufacturer, and is prima facie evidence that the manufacturer has sold or intends to sell the motor vehicles on the condition or with the agreement or understanding prohibited by this chapter.