Indeed, there is always a problem when one determines the conclusion of any argument before actually considering the evidence. When one does this he becomes blind to any evidence that does not fit into his pre-conceived conclusions.
Agreed. People can be hindered from the truth by their own confirmation bias. I have become keenly aware of this myself over the years and will listen with an open mind to pretty much anything (except heresy and doctrinal error). So I get attacked by both sides of many issues because I will accept arguments from both sides as valid, and reject others as invalid. Even though I initially did not believe in flat earth and thought it was preposterous, I made a point of looking at the evidence they presented ... while rejecting the emotional rhetoric and
ad hominems on both sides.