Earlier quoted context omitted.
It isn't immoral or unethical to have sports where long-term injury can occur. Using that metric we would have to ban all sports. What is unethical is not educating the participants of the risks. We need to push for more studies and education, not bans.
We (society) typically require someone reach a certain age of consent before we allow participation in life-altering activities. e.g. drinking, smoking, driving, enlistment, marriage, tattoos, etc. A 13 year old jr. high schooler who wants to play for their school's football team isn't able to fully assess and weigh the risks of long term brain injuries from an activity. Maybe parental education and consent is enough…
And for the highest levels where CTE is a risk, players are compensated for the risks they take in playing. No one compensates you for smoking or drinking.