One of the things I've come to realize over the last few years is that it is very difficult to change somebody's mind. This can be enormously frustrating, especially when you are convinced you are correct and you can't understand why other people can't see your point of view. As we've come to understand more about how the brain works we have learned that very few people actually form their opinions by examining and evaluating evidence. Instead, most people have fairly rigid mental frameworks. Information either fits into the existing framework, or it is discarded.
We visited a couple of Agros villages last week and learned first-hand how mental frameworks can mean the difference between life and death. I had always assumed that most cultures understood the link between clean water and health. It turns out that this is often not the case. It is remarkably hard to convince people that their drinking water may be causing them to get sick. Bacteria are invisible, and contaminated water often looks quite clean. It even tastes better then boiled or filtered water. As long as the water isn't obviously dirty it is very hard to prove that it could be linked to disease.
We can blame superstition and lack of education, but we aren't any better. What would it take to convince your parents to become vegetarians? Have you ever convinced somebody that their political or religious beliefs were wrong? People see the evidence they want to see.
How do you convince people that their water may be harmful? There is unfortunately no easy answer. You could try to educate the youth. You could drag a microscope into the field and show people the bacteria ( but this would be expensive and time consuming). You could hold classes for the adults (but they might simply not believe something they can't see). It's a remarkably difficult problem, and it kills tens of millions of people a year.
You can bring a village clean water, but you can't make them drink it.