We all assume that we are all in the same place, in the same frame of mind in every way. That we're all of even maturity (both physically and metaphorically), and that we are all starting from the same knowledge base. And instead of stepping back and saying, "hey, he doesn't know, maybe I should show him what I've learned?" we result to namecalling and insults, blaming each other of "lack of empathy" or needing a "mental crutch."
If I look at someone who disagrees (or is straight out wrong, in that they are ignoring commonly held facts) with me, at the very least I can step back and figure out why...
Where is the poster from?
How old are they?
What are their hobbies?
What do they base their morals/beliefs on?
What is their level of education, and what is it in?
I mean, just in knowing that, it is easier to view your opponents with a different perspective. I had a professor once tell me that she (a bleeding heart liberal) tried to convince her father (die hard conservative) to switch to solar energy for their house on environmental terms, and he would not accept it as reasoning enough. But when she told him of the cost savings, and explained it in a way he could relate to and cared about, he got the solar panels. As elementary as this sounds, its a good lesson when debating especially when butting heads with someone who hasn't listened to your perspective in the past.
Not only does this lead to more meaningful debates, but mutual tolerance.