Look at this article (and similar ones). Pull out the negatives and make them into positives for your arguments --
Winning and Losing | Psychology Today
Like this --
1. Children need to win (winning = pride, losing = shame)
2. Children need a creative challenge to make up own rules and cheat so they can boast, otherwise they will refuse to play
3. Children, especially boys, need feeling of physical and intellectual dominance
4. Children need to believe they can do great things
5. Children need encouragement to be their fantasied selves