I can't point to a particular time, place or conversation where I learned this fact, but I remember being encouraged by my parents that it is dangerous to accept everything taught from a lectern or pulpit without question. No matter how well intentioned the teacher, sometimes they make mistakes and sometimes they misinterprete the data. No matter where you are, school, religious gathering or watching/reading the news media; do your own research. If nothing else, ask questions about their sources and motives.
Not all sources are infallable; text books and the words of other teachers, for example, can have agendas and wrong presupositions. Some, when presenting ideas that are widely debated, do not present both sides or even acknowledge there is a debate and allow the reader or listener to make an informed decision but, only present their beliefs for people to swallow without question.
Many of history's great tragedies begin with someone taking advantage of uneducated or under educated people to cause them to depend on a corrupt leadership and trust them unquestionably only to wake up one day to the reality that they have, in fact, been dupped by someone's charisma or charm and enslaved or sacrificed. This has happened in both government and religion.
If you are a Christian, know your Bible, understand where it came from and how it has been tried, tested and proved. It is one thing to be lead to believe false things about your government, history or business it is entirely different to trust your eternal soul to just anyone. To follow your beloved pastor teacher without question can lead to an incorrect view of God, humanity, personal value etc. That can lead to either a very frustrating and discouraging life or eternal damnation. It is not always senister sometimes it is just misdirection but, it is too important to ignore.
There is no need to be disrespectful about it, I must add; read, study, pray and ask questions humbly. Do not respond to any error with arrogant animosity however, prayerfully consider and give the proper response to the situation.
Ask questions, if only of yourself. Find answers from proven sources. Be willing to exercise a little faith but don't check your brain at the door because solid faith has reasonable substance.
