In my teaching of science to high school and college students, I emphasize the need to have good evidence and sound arguments. However, at some point I also need to teach them that ultimately not everyone cares about these things. Those who oppress people don't care about evidence and arguments, but the oppressors will use such things to exploit people. Thus, the primary role of knowing good evidence and sound arguments isn't about changing the mind of the oppressor, but is about protecting yourself from oppressive tactics. Oppressors who have already made up their minds won't be swayed by evidence and argumentation, but that doesn't mean that they won’t be brought to justice or be disarmed by these tools.
People have the uncanny ability to deceive themselves, along with each other. This is why we say that people are "in denial" about their circumstances. As a human rights advocate, scientist, and science teacher, I know the importance of having good data and sound arguments in promoting the rights of exploited people. Good research papers can make a societal problem concrete, forcing opponents to face the facts – denial that the problem exists is a way of stalling progress. Good data can change policies and bring forth much needed funding from governments or private sources. But good data isn't enough. As the saying goes, "Statistics don't lie, but liars use statistics." Therefore, good data needs the help of sound arguments that correctly apply the data and to counter the misuse of good data.