Pride And (Internet) Prejudice

Why is it that when we see something on the internet and feel like we disagree with it, we immediately tell the person posting the content that they are wrong? Shouldn't we at least assume that we may not fully understand their position? And if we make that assumption, shouldn't we proceed by asking them to elaborate on why they hold that position rather than our own? Perhaps I am naive, but it seems that this one simple step would dramatically change how we view and interact with on another.