We also helped our cause immensely through the use of subliminal messaging ... oh heck, let's be honest here ... there was nothing subliminal about it. We came right out and said that it was too dangerous (as were snow boarding, skate bording, and a list of other sports and activities that could cause great bodily harm ) and strongly ... very strongly ... suggested it might not be a good idea. Of course, if he had elected to play an additional sport, we would have brought out the "Other sports for baseball dummies" book and learned what we could as a form of parental support. Fortunately, our son was very impressionable (it helps to start when they are 5 or 6 with those messages) and other than a couple of attempts at basketball and that 'other' sport played on a grassy field, he focused all of his attention on baseball.
(*That was an actual typo that I spotted only after I posted the message ... it is still early here )