Sport has shared rules and agreed outcomes
Being in a contained area which, while contested, is nevertheless bound by rules and conventions, and is adjudicated by a recognised and impartial referee goes some way towards ensuring that those used to, or who are seeking, a world without norms and without rules can be countered, both conceptually and literally.
The similarities football, and some other sports, share with peace talks and other forms of dispute resolution are manifest.
At another level, playing in a team with others with whom an individual might have been obliged to fight and or to hate, can provide ground on which mutual understanding and compassion can be gained.
The most basic rule of football is that hands cannot touch the ball. This is understood by seemingly everyone, boy or girl, over the age of about 7. In understanding and accepting such rules, especially ones which are reliant on unnatural habits, such as using feet not hands, can underline the value of seemingly arbitrary rules when made in mutual agreement with another party for a shared outcome, a vital component on the journey to peace.
The inculcation of a rules based system, which is vital for a game (in this case) to go ahead, to the collective enjoyment of all, allows individuals to accept the validity of rules that may apply to post-conflict scenarios, for instance.