You're having a debate over a matter of scriptural interpretation. Does water baptism save or is it merely something that comes as evidence of faith in Jesus? Your opponent begins to list his or her qualifications that give authority to their argument. What do you do?
Every man or woman must have their own personal faith before God. That means everyone must make up their own mind in the end. Does that mean you should listen to someone with more authority, believing their position because they are more qualified than you?
Part of being human is being fallen. Everyone is capable of mistakes. However, qualifications should give you pause before you reject what the qualified person has said.
The best qualification is not a degree, or a piece of paper with an amazing seal on it. The best qualification comes from wrestling with the issues prayerfully, and following the truth where it leads: learning to listen to your conscience, your intuition, and those who are closest to you... and when to reject those same things as being misinformed.
The spiritual person exercises their discerning with care, and understands where they are weak. The spiritual person seeks wisdom from God because they know there is danger in folly.