My reaction is more visceral: F 'em. I wouldn't spend another iota of attention or $$ on them.
Use the reaction two ways: (1) to map out improvement, and (2) motivation to pound their collective heads in sand.
My sincere hope is that 2018 gets to a point where he can face said school on the field and burn their asses.
This is my first response as well, but on second thought, I wouldn't close anY doors. I wouldn't waste any energy on them, but I wouldn't burn any bridges. If the RC was to initiate contact again, I would express my concerns about the HC's apparent non interest and see what he says. If it is positive or negative then you have a path to proceed. If son is not contacted by them, than I would move on and hope to play for a team that I could regularly stick it to them. My gut feeling is that you are wasting your time with them, but you never know. Good Luck!