No, if people want to damage their own brains willingly, then that is their choice. It's not like they are forced to partake in the sport, and as a result, they should be well aware of the negative potential implications it may cause them.
No. Boxers are aware that it's a dangerous sport, so if they want to take the risk and box, let them. Also it's an entertaining sport. Who doesn't like to watch two guys beat the **** out of each other?