The rules are there for safety.
Sorry to hear about your son, and agree for the sentiment. Technical point (not a criticism), but the rules actually aren't there for safety. If they were, then FIFA would adopt separate rules for the game for youth, teenagers, adults and pros. But they don't. It leads to the arguments therefore about whether a ref should call an AYSO game tighter than a pro ref would call a pro game. And therefore the complaints (somewhat legimately) that kids need to be taught aggression as they move up the ladder.
The rules surrounding fouls actually have more to do early on with distinguishing association football (soccer, played with the foot) from rugby or gridiron football (played with the hands) in the late 19th century. In the earliest games, tackling was allowed. But as the game diverged from rugby the rules diverged as well. In 1871 there was a meeting of the clubs in England...those that wanted to play with their hands and tackle were outvoted and left to form the Ruby Union, while the others adopted the rules which started to resemble modern football. Incidentally, a lot of that is also where we get the careless standard...it's from old English law which generally assume if something happens (such as a player going down) someone must be at fault because in nature players don't typically fall down (the best modern analogy is car accidents...there's no such thing as "just an accident" typically someone being at fault)...but that led to constant whistles which led to the trifling bandaid being placed on top of it.
Nerd moment over. You may resume.