You are right that reading and writing can be verbal jousting but that is not the sole purpose of reading and writing. When dealing with the written word you have a record front of you that you can analyze and look for confirming information to see if the words are manipulation, truthful or outright lies. having words in front of you that you can go back and verify that your memory is correct gives you an opportunity to think more clearly and gather information so your better informed.
In a debate, the words fly by, they are half remembered and you come to conclusions that are not based on what was said but instead based on what you heard and half remembered.
there are two groups of people affected by the ephemeral nature of a debate. First is the group that listen but don't necessarily seek out a transcript. The second is the other person in the debate. They have to hear and respond in a matter of seconds. interaction is why I say say debates only prove who is the better debater.
In a debate, the words fly by, they are half remembered and you come to conclusions that are not based on what was said but instead based on what you heard and half remembered.