Everyone has their own opinions, and we all think our opinions are correct. That does not necessarily make one a fool. But there is a difference between having an opinion and being opinionated. Take a look at this proverb:
Fools see their own way as right, but the wise listen to advice.
There are some people who absolutely know they are right. If they ask any questions from someone, it is only to validate what they already knew was correct. These are the fools about which the proverb warns us. They ask questions, not for advice, but to prevail.
The hard part of fools like this is when they are in the Church. It is hard because it is so disappointing. We are called to be disciples of Jesus Christ. The word disciple means learner. If we cease learning, we cease being a disciple. People who already know all there is to know are no longer disciples. They are fools. This is because Christianity is a relationship with an infinite God, so there is always more to learn.
Of course this does not only refer to knowledge. We learn through experience with God, through God working in our lives. When people feel they have experienced all there is to the Christian life, they become fools. When people cease having a living and vibrant relationship with Christ, but rather have stagnated and do not seek to grow, they become fools.
The best approach to the Christian faith we can have is to live our lives with the truth that we do not yet know all there is to know about the faith, we have not experienced all there is to experience with God, and we can always have a more intimate walk with God. When we keep these as core precepts of our faith, then we will always be open and seeking advice from the wise–those that are ahead of us on the way.