There was a rule against facial hair for players on UCLA basketball teams.
One day Bill Walton came to practice after a ten-day break wearing a beard. I asked him, "Bill, have you forgotten something?"
He replied, "Coach, if you mean the beard, I think I should be allowed to wear it. It's my right."
I asked, "Do you believe in that strongly?" He answered, "Yes, I do, coach. Very much."
I looked at him and said politely, "Bill, I have great respect for individuals who stand up for those things in which they believe. I really do. And the team is going to miss you."
Bill went to the locker room and shaved the beard off before practice began. There were no hard feelings. I wasn't angry and he wasn't mad.
He understood the choice was between his own desires and the good of the team, and Bill was a team player.
I think if I had given in to him I would have lost control not only of Bill but of his teammates. (From "Wooden: A Lifetime of Observations and Reflections," published in 1997 by John Wooden.)