The moral differences between modern America and the whole history of the West have a lot to do with the fact that modern America places individualism ahead of the whole, and throughout the history of the West the health of the society as a whole was typically seen as more important than the rights of individuals.

Modern America will sacrifice the health and long term success of the whole society for each individial's rights. Throughout most of history, people would rather sacrifice small groups of individuals for the health of the whole society. Which model is better is debatable, seeing as the world has never come to an agreement on it, and we don't have a lot of data on this recent model.

In the opinions of the people in question, castrating a small subset of the population was better than the alternative, which was venereal diseases spreading like wildfire through society, with that small subset of the population leading the charge. It wasn't as simple as "we don't like people who are different so fuck 'em." Their whole sense of morality rested on completely different substrates than that of modern Americans.