John, you are correct that there is much more behind a difference between using “I” instead of “we” in presenting reasoning in persuasive writing.
By using “I” the author emphasizes the strength of the argument. It manifests disregard for how many people might have a different point of view. It declares a conviction that presented facts and logic can stand on their own.
By using “we” the author subtly implies that the strength of the argument arrives from the popular support. The strength of argument comes from the implicit assumption that the majority has to be right. In result, it infers that smartass authors using “I” in their reasoning should be ignored.