There's one way Prewitt could have gotten Holmes off his back...
He could have agreed to box on ONE unyeilding condition.
He would say, "No Officer should ever expect his men to do something HE would be afraid to do."
So Prewitt says he will only box for the regiment if Captain Holmes agrees to be his sparring partner before EVERY match.
"We take our uniforms off and step into the ring man-to-man. There'll be NO
insubordination on MY part or pulling rank on YOURS.
Those are my terms...take it or leave it."
That way Holmes would have had to put his money where his mouth was and therefore either back off or accept.
And at least Prewitt would have satisfaction before every match; pummeling a superior officer with impunity.