Another point to bring.
Geneology is often based on information passed down the lines from various family members. It is a difficult area, as even the most meticulous research may result in conflicting information.
Even when you are 100% sure in your mind that the information you have received is accurate, you must temper that knowledge with the fact that in most cases, we were not there.
All we can do is our best. Accept the input from the other person, and rather than it becoming a heated situation, try working with them so that both of you can reach a concensus, even if it is to admit that neither of you is really sure.