find it against one's conscience; too proud to do
A formal, somewhat literary expression used when someone refuses to do something because they consider it dishonorable or beneath their dignity. Often followed by a verb in the negative or a phrase indicating refusal.
See also: 潔しとしない
He found it against his conscience to win by unfair means, and gracefully admitted defeat.
She is too proud to speak ill of others, and always remains silent.