I never found debating, whether in the forums or formally, to be an experiment in truth-finding. Most people, even if they subconsciously recognize mistakes in their arguments or thinking, tend to double-down on their original, fallacious reasoning. People value others who are right, and ostracizes those who are wrong. This is one of the main reasons that people never apologize, admit their incorrect assertion, or correct their original arguments. Usually the response from others in recognizing a fallacy or error of reasoning is to ridicule the guilty party by declaring them stupid or unreasonable. This, in turn, leads to the perpetuation of the social ailment. The forums are not invulnerable to this conundrum; perhaps causing countless flame-wars.
Also, the more that people identify with their political affiliation, the more likely they will feel personally attacked when an opposing side contradicts their ideas. In reality, much about politics will never affect us. Most of us are not destitute to the point that we cannot access the internet, most of us could get a low-paying job if necessary, and most of us have graduated from high school and are thus more likely to earn more in comparison to others.
I find formal debates comforting because you never have to be right, admit your personal ideology, or care about the people that would be affected in a debate-able topic. It is essentially a Chess game where the pieces are contentions, and tactics can be used to defend or attack other pieces.