Even if you are right, will your son listen to reason? And the broader question is, has it ever occurred to you that neither of you is right? Gasp! How could that be? Actually, you are much closer to right, while your son is tragically wrong. He can be excused, however, because he's just following the advice of 95% of the cookbooks that deal with braising and stewing.
The issue is so complex that food science writer Harold McGee devoted an entire chapter of his book The Curious Cook (Canada, UK) to the question of whether to simmer or boil. One of the first issues involved is whether you're cooking a small, tender cut of meat, such as a pork chop or a fish fillet or a large, naturally tough roast such as beef round or chuck.
There are two opposite forces at work when you cook meat in hot water. One process squeezes the water out of the meat, making it dry and tough. This process begins at the shockingly low temperature of 105°F (35°C), and half of the meat's water is driven out between 140°F and 160°F (60°C and 71°C). The other process is that the collagen - the connective tissue that binds the muscle fibers and makes important muscles tough - doesn't begin to break down until 160°F (71°C) and doesn't dissolve into gelatin until it has been cooked at length above 180°F (82°C). When that happens, the muscle fibers loosen up, the meat is actually able to reabsorb some of the liquid in the pan, and the texture of the gelatin produces the sensation in our mouths that the meat is again fairly moist. It's not really; it is much, much drier than it started out, but with enough cooking, these tough cuts of meat become much more palatable.