I'm so sorry this happened to your son. It sounds as if he did nothing wrong, but an experience like that would be hard to live with.
I'm stunned that team parents told their kids not to throw with your son. Those folks sound both stupid and cruel.
My son is in HS and now throws hard enough that I am really on my toes on the rare occasions he is willing to play catch with me. I don't think he'd hit me in the face, but during long toss it is easy for an old guy like me with slow reflexes to take a short-hopper off the shins. Lately the boy thinks it's funny to throw breaking balls to me without warning. The other day I said "Think for a minute about how you'd feel if one of those sliders you are practicing hits me in the ribs." He immediately came back with: "I'd feel really bad... [smile and a pause]... Because that would mean my dad can't catch." 