Disappointment is a fact of life, something everyone will often encounter, but no matter how old we are the experience is, well, disappointing, LOL. As parents we want to give our children everything that they need and maybe all that they want, but we know that for many reasons this is not realistic.
Mom, your refusal to allow your son to play football resonates with me, because my husband and I refuse to allow our son to play football due to the potential for brain injury and the hypermasculinity and misogyny that often go hand in hand with football.
You are well within your rights as a parent to protect your child from documented risks. The NFL acknowledges that there is a link between football related head trauma and chronic traumatic encephalopathy among professional players.
You understand the risks, but your son just wants to play, so he is probably not hearing you, but make sure that you listen to him and validate his feelings and try to clearly explain to your son why you do not want him to play. Together you all can research the risks and turn it into a presentation for family and friends. Hopefully this activity will allow your son to understand, why you refuse to allow him to play, even if his mind is not changed.
Have you all discussed other sports? Would flag football suffice? Touch football? Maybe Soccer? What about Lacrosse? Are you willing to allow him to try different sports so that he can discover a new passion?
Like most children, your son is going to try to wear you down, if he is not swayed from playing football. Hopefully you don't take the requests personally. If you do, please don't. His asking has nothing to do with you. Playing football is important to him, so he asks because he wants to play, so remain mindful of this in your response. Keep in mind that if he goes to college he could always walk on a team and play. If this happens, all that you can do is tuck away your disappointment and support your son in an activity that he loves.
For now though, validate and affirm your son's disappointments and feelings and help him to find another sport or sports to play.