I appreciate all who have commented. I have an update, in addition to comments from some of the above posts. I do understand some of the general sentiment around ideas of spoiled 10 year olds and their parents being oblivious to the fact that they suck and demand they play, however:
While I understand the importance of teaching kids life lessons, I kind of question the idea of going Tyrone Corbin on 5 year olds. I think I'd share a lot of these same sentiments if these were 12 year olds, but not at the age of 5. To be clear, my kid is a pretty good player. I taught him by pitching to him (which brings me to my tangent of t ball... when I played at his age it was coach pitch and you only used the T if you couldn't hit from the coach... speaking of life lessons, let's get rid of the damn T and let the kids play real ball, but I digress). He'd never hit off a T before, but if you saw him hit pitches you'd think he was pretty good. In any case, any of the mistakes he's made are the same mistakes every other kid has made. The idea that him seeing time on the field is conditional on some coach's arbitrary measure of success, two games into the season, is poppycock. I think him being "skillful" as a prerequisite to playing as a 5 year old is irrelevant (or at least should be in the minds of rational people). Baseball varies quite a bit from other sports in that nearly the whole team should be on the field at any given time. It isn't basketball where at least 7/12 people will be on the bench at any point. To justify sitting 4/9 innings based on any measure is total ********, especially when lots of other kids haven't ever sat out.
Also, it was mentioned about how if he played it essentially is just passing the buck as someone else's kid will sit on the bench. I'm not advocating anyone sit on the bench, especially not a significant amount. As mentioned, with this being baseball, there's plenty of field-time available with people only having to sit out an inning periodically. I'm also not advocating my kid play 100% of the time. I'm just advocating he not sit on the bench in a figure approaching 50% of the time, or even 25% of the time as that is not necessary nor required -- for anyone.
As far as taking his career as a T-ball player seriously, my thoughts mirror Buck Russell's thoughts on taking a career as a student seriously (highly recommend viewing as this is very pertinent -- start at 0:41):
https://www.youtube.com/watch?v=xEt5dEOcW0I
The update:
So Friday evening I called the coach. I spent the first part explaining that I understand it's difficult managing a bunch of kids, etc., etc., and then expressed how my concern was that my kid sat out multiple innings the first game, and that when he asked me why I told him that everyone is going to sit out at some point; but then the next game, when only 10 kids showed up, he still sat out half the game. He mentioned that it was an oversight and that if he had known he sat out in the first game that he wouldn't have sat him. I found this somewhat disingenuous as it was him who specifically sat him out the second game in more than one inning. If you've only got one guy on the bench, it's hard to make that argument that you don't realize the same person is sitting out. I'm willing to grant that game-to-game it's easy to not recognize that. Not so much within the game when you've got 10 guys. Later in the discussion he came back to "well, he did watch two balls go by him," so obviously he recalls that. He did, however, have to admit that this was the same problem with all the kids.
So yesterday there was another game. We were the first ones to show up. When someone else arrived, I overheard the coach state that they were only going to have 9 guys at the game. Later, before the game started, he approached me and told me that he'd be playing the whole game.
So far, we're 0-3. I attribute this to the defensive strategy (not that there should be one for a bunch of 5 year olds playing T ball), but their game plan is have the pitcher (in T ball the guy who gets 75% of the hits coming to him) field the ball and then try to run down the runner, without ever making an attempt to throw the guy out. I assume that since they'd risk an error from throwing or catching at 1st ended up in the runner taking second, that they think it's a better strategy to have the kid try to run everyone down rather than throw to another kid who may not catch it (or the pitcher may not even throw it good). Anyway, for the 3 games this has been the strategy. The entire game there was only one occasion where the ball was thrown to first, and that was by another player. Now, I don't really care about game plan (or if they even have one), but if you're trying to "win" games by not really having the kids develop any skills (i.e. simple fundamentals by throwing it to first) and instead are relying on something that's not a sustainable talent (running guys down), and which isn't working anyway (0-3), then that's just silly.