How Do We Know What We Know?

Propaganda is not something limited to other cultures, or even the past evils of World War II. Yes the Nazis and Hitler specifically used it greatly to their advantage in convincing the German youth to kill. And Radical Islam teaches the same message, to kill, to young children. But what about the Christians in America? K—and D--- have spoken about their recent understanding of “how we need to stand up and support Israel because they are God’s people.” True enough in words, but does that support actually mean killing the Palestinians, over land that 80 years ago belonged to Palestinians- some of whom are Christian and Jew, all living peacefully together in that land. They are both gun ho about supporting Israel financially and through military donations because of something they have heard a Bible Study leader say. Yet I came back from the Middle East not so keen on the support the U.S. provides because of something I heard a professor and several political aides said. Are we so easily swayed that all it takes is one speech to form an opinion? I want to make my own decisions, but I don’t know what sources I should and can trust.
It is remarkable how even music can change a worldview. With the right music in the background, a scene, an event, a speech can become good or evil- without the words changing. What happened to thinking about what we are taught? Not everything an authority says is gospel. In fact, shouldn’t we even question the gospel? After all, if we never question who God is and what we are taught about him, then we never seek him and thus never actually form a relationship with him.
So I want to check and double check and research what I see and hear. Unfortunately the only resources I have to check with are those written and recorded by other biased humans. So I can only check a bias with a bias.