Golfman, i think that the general consensus among most coaches is that after a tough loss you should mostly just talk about the little things you did succeed with in the game and try to reinforce the positives and not send everyone home on any worse of a note than the loss itself. It is certainly not a good time to call out individuals..learned that one the hard way. Thank goodness it was a resilient kid.
Personality traits are a part of the game, they can be contagious, and can be a blessing or a curse depending on the trait and the player. these need to be coached and reinforced just as much (sometimes more) as any part of the game. you don't think that pitchers need coaching with their composure on the mound, for instance? A freshmen making an executive decision to try and steal in a textbook bad situation without a sign is certainly a violation of team rules. I think we can all agree on that.
I see the kid stealing as a mental error made by a "rookie" not a violation of team rules. I'd be more concerned that he made his mistake at 100 mph and didn't hesitate. On the field mistakes should not be "punishable." They should be learning experiences. If you try to control every little thing, you set yourself up for bad situations.
An I do think pitchers need coaching about composure on the mound. But when they loose that composure is that a time for "punishment" or coaching?
Being a good teammate works both ways. If a kid makes an error he needs to own up to it. His teammates don't need to get down on him, but if the pitcher gives him "that look" he should accept that look. But then the pitcher needs to go back him up. It takes a lot of conversation to instill good teammate characteristics in growing boys. I don't think you can punish you way to being a good teammate.