Chair,
To answer your question.....
Here is what I surmise of TH's position:
He focuses very narrowly on this kid's stellar arm. He views moving him up with older players is a good thing, because it's more of a challenge for this kid and will only further develop his already considerable skills. On this VERY narrow front, he raises a good point.
However, this issue is WAY broader than the 1 facet where TH makes a point. All of this has pretty much been fleshed out at this point and we are now beginning to repeat ourselves.
The other side to TH's point seems to be one of 'creating fairness' - which is an arbitrary thing and is usually an unconscious (although sometimes conscious) attempt to create 'sameness'. Call it limp-wristedness, call it pussification, call it Marxist tendencies, call it well-intended, or whatever. I don't pretend to fully understand his motives.
We've had similar, sports-related discussions in the past and TH seems to have a real problem with kids competing to a point where they want to be the best. His problem with this seems to narrowly focus on physical activity as I don't think he's ever expressed an issue with scholastic achievement. He seems to be really concerned with taking competitiveness to an ugly level - you know when that old adage of 'it's not whether you win or lose but it's how you played the game' gets thrown by the wayside where winning is the only thing that matters. Yes, some parents instill this to a ridiculous extreme, but a majority do not - it's just the rotten apples who get the spotlight leading some to believe that most parents are like this.
Anyhow, after refusing to address all of the other expressed negatives regarding to moving this kid into a league where the other kids are 3 years older, he has moved up the abstract scale to his usual demons.
It's his general attitude on this that leads to (I am not saying he feels this way as I am now moving the goalposts) laws enacted to prevent suspected criminals from being wrongfully imprisoned (which is always tragic) but makes the job of prosecuting true criminals so difficult that for every 1 non-criminal saved from wrongful imprisonment we have 10 true criminals walk free to prey upon future victims. Sometimes we have to weigh the positive and negative tradeoffs and people who think as TH is espousing here always seem to fixate on the 1 negative and try to right that without contemplating, or caring about, all of the negative tradeoffs associated with the enactment of their view.
That's about the extent of my understanding of his position on this.