I understand that baseball is a team sport. I am all for the "wherever you need me coach" type of player. But, I can't agree with putting a kid on the mound that doesn't want to be there. When I coach young kids, 9-12, I tel them all at the beginning of the year, I plan on having you pitch at least one inning. A lot of kids say "Well I've never pitched"...and I tell them, well, I want you to experience what it takes to be a pitcher, maybe you'll like it maybe you won't. I have had kids try it and like it. I have had kids try it and say "never again", and I've had kids refuse to do it. The ones that refuse, I did not push, just left the door open for the opportunity when they felt comfortable enough to give it a shot.
Why put a kid on the mound when he doesn't want to be there? You're risking the chance of evoking a bad attitude out of the kid and then having it spread like cancer, especially at 12. IMO, in the OP's statement, I don't recall them saying their kid would only play a certain position, just that he didn't want to pitch. I don't consider that being selfish or anti-team. Forcing a kid to take the mound, IMO, is a bad move. There is no real upside for it except for the Coach exerting his authority.