No, it is never acceptable or legal to intentionally bump a motorcycle rider with the bumper of your car or any other vehicle. Intentionally hitting or causing harm to a motorcyclist is considered a dangerous and illegal act, and it puts the rider's life at risk.
Motorcycle riders are vulnerable on the road due to the lack of protection compared to occupants of cars or other enclosed vehicles. Any intentional contact or collision with a motorcycle can cause severe injury or even be fatal to the rider.
It is crucial to always prioritize the safety and well-being of all road users, including motorcyclists. Treat them with the same respect and courtesy as you would any other vehicle on the road. If you encounter a situation where you are concerned about a motorcyclist's behavior or actions, it is best to contact the appropriate authorities or report the incident, rather than resorting to dangerous and aggressive behaviors yourself.