"presentism /'prezen,tizəm/ n. uncritical adherence to present-day attitudes, esp. the tendency to interpret past events in terms of modern values and concepts." -The New Oxford American Dictionary
In the history field, we constantly hear "I would never do that!" But, it is far more complicated than that. Just like many of us would not harbor a fugitive today, many people understood the real 1800s risks of harboring a fugitive slave.
Today, very few of us would let a doctor operate on us with the fresh blood of another patient on his arms and apron or squeeze their internal organs to get a tiny waist.
Information and knowledge builds upon existing knowledge, things that are obvious to us or "common knowledge" may not have been to people in the past. Today, every child knows that germs can make you sick and that washing your hands can keep you safe. Three-hundred years ago the technology to prove the existence of germs didn't exist. People responded to the modern scientific and medical information at their disposal.
People in the past were not any less intelligent than people today. In 300 years, schoolchildren everywhere will laugh at the stupidity and ignorance of the inhabitants of 2012. You cannot judge people of the past by modern standards, values or ideas, you can only try to understand them through the lens of the time period in which they lived. Many people fall into this trap but study can help create a fuller understanding of the people of the past, what motivated them, and their experiences.