Human Rights evolved

The development of the idea of human rights is often credited to the enlightenment era in Europe, when the dignity of the individual was promoted and the pursuit of scientific knowledge became valued over superstition.

Once this quest for knowledge began, it was only natural to also challenge preconceptions about other people as well. Since then, the overall trend has been to downplay the "otherness" of different people and to expand our sympathies with those who don't look just like we do.

Steven Pinker's "The Better Angels of Our Nature" does a wonderful job of disputing the perception that the 20th century was the most horrendous by comparing it to humanity's long and often brutal past. Brutal not just in the number and intensity of wars, but also in everyday life.

In the course of tracing this decline in violence, he also describes the development and advancement of human rights.

I don't necessarily think there was really a widespread ethos of "do whatever you want", but there is certainly an awareness of how our actions impact the larger community.

As a last thought, the fact that people travel so much more now and have technology like the internet means that we are more in contact with different people. It's much harder to maintain a prejudice when you have frequent interactions with other people at work, school, and so on.