Share buybacks are necessary to provide companies with stock for incentive and stock purchase plans for their employees. Since the stock is purchased on the open market I do not believe it artificially effects pricing.
The sponsor of this bill believes that companies should share profits with their employees. If you enact this legislation then you will be tying a companies hands regarding profit sharing. Most companies give or sell shares to the employees. Since there is a finite amount of shares issued, companies need to periodically go to the open market and purchase them.