Clearly she'd touched on a sensitive nerve. There were plenty of disgusting monsters amongst the Death Eaters who lived for attacking helpless women and forcing them to commit depraved acts that made even Hermione uncomfortable, and she had a pretty open view about sex. Of course, as too many people weren't aware, rape had nothing at all to do with sex and everything to do with power. The slime who enjoyed those acts were allowed to thrive during the chaotic, violent early years of the regime, but most of them were either killed in the pursuit of their depravities or ordered by the Dark Lord to cease and become respectable members of his new society. Despite sexual violence being an all-too-common occurrence in societies like theirs, many men who believed themselves to be morally superior or who possessed a strong sense of honor abhorred such acts. There was a code amongst the Death Eaters. Those who committed such vile acts were relegated to the bottom of the heap and scorned. By asking Rodolphus if he had to force Ginny, Hermione insulted him gravely. He likely wouldn't get over it any time soon, if ever.