I believe it's an oversimplification to see this plot choice as romanticizing, minimizing, etc. the choice Daphne made.

Again, context is important. This is a fictional account of British aristocracy in the early eighteen-hundreds. These were people who were obsessed with social etiquette and "good form". This is a world where a woman's reputation (along with her future prospects) could be destroyed by a concealed unchaperoned meeting and a brief kiss.

Fast forward to today. The Duke could have traded one conflict for another by simply getting a vasectomy. Thus, removing any potential controversy about rape. Different age, different conflict.

Humans evolve slowly. Ethical code evolves slowly. Pretending otherwise makes the task that much harder.