The idea that “I’ll believe what I want to believe” and “you believe what you want to believe” can sometimes lead to the avoidance of the truth. You should seek to understand the viewpoints of others. Getting to know someone better provides you the opportunity to build upon the things you mutually share or agree, instead of putting all your energy into disagreeing.
Whenever you see people arguing as if it were intellectual combat, the nature of the argument can be grossly misunderstood or overshadowed by the person with the loudest or most convincing delivery. Instead of taking offense to someone agreeing or disagreeing with you, be willing to keep an open mind if the argument has good merit.