The need to be “right” stems from ego. However, there's much more to it than that, isn't there? Being perceived as “right” in our opinions and lifestyle choices is not just important to our ego. Feeling as if we are “right” impacts the decisions we make as to how we live, who we share our lives with and more. Whether or not we feel our opinions are valid shapes our lives.
What convinces us that our opinions are correct? More often than not, it's validation from other like minded people. Scientifically proven factual information would be a more accurate representation of the truth. However, the human ego sees agreement as validation. So we spend endless hours seeking that validation. Which is one reason we are more comfortable around those who agree with us.
Taking the thought further reveals the essence of herd mentality. Those who manipulate the truth to their advantage have been using herd mentality for centuries. Convincing large groups of people that their opinion is the truth serves them well. Label adherence to your creed as loyalty, faith or patriotism and people will follow blindly. Cults, religions and nations alike depend on this for their existence.
Still, it doesn't change the truth. The truth will remain accurate regardless of how many people believe it. Therefore, in some ways, convincing others of your opinion is pointless. Yet, we persist. Why? Because life is about connections. We are all connected. Hive/herd mentality has power over us because it's the basis for all life. We are drawn to it like moths to a flame.
Of course, that's just my opinion.