All good knights held it after, saw: Yea, sirs, by cursed unknightly outrage; though You, Gauwaine, held his word without a flaw, This Mellyagraunce saw blood upon my bed: Whose blood then pray you? is there any law To make a queen say why some spots of red
This refers to the mannerisms and politeness that men in the Victorian era must uphold towards women. Victorian men must be pleasant and pleased women; however, at this scene, Morris uses Sir Guawaine and Mellyagraunce as a contrast to that ideal. https://www.jstor.org/stable/10.1086/427127