I don't have a kid in football (I have a six year old girl whose idea of sport is pretending to be a unicorn). But I know that in HS sports in general they have safeguards in place (divisions etc) to make sure that we don't end up in a pee-wee plays Patriots type situation. When those safeguards fail, then we no longer have the same expectation of injury -- the expectations drastically change compared to what I signed up for.
These are probably kids that love football, and love the game, but not so much that they want to elevate the risk of concussion above a certain threshold. Frankly this seems perfectly reasonable, given the sport we are talking about. If they quit just because they were worse, and it was chess, we wouldn't be having this conversation.
Everyone has a line where pride becomes folly. Deus/Kontradiction, where are your lines? Or would you rather die than give up? Would you rather your child die than forfeit? I'm saying this to make the conceptual point that there has to be a line (unless you are just crazy or morally beyond reach). The question is where is it for you? If you were in MMA would you rather have your arm broken than tap out?
Frankly it seems this School of Giants needs to go to a different division, because this is the third school they were scheduled to play that is forfeiting. This suggests something has gone wrong with the system. Problem is there may be no other options in the area: they are playing everyone they can, but they also have recruited everyone in the sphere of elibigle players. So it is pretty much an unfair advantage. Everyone else is pretty much like OK screw you you can go play with yourself in the corner if you are going to just recruit every above average player in the region. We will play each other and you can go jerk each other off.
Sort of a nice ironic twist. This is sort of the underground storyline here it seems.