Yes but his point is this "If something happened but you can't prove it to someone else, it really didn't happen". And that is Reason???
Stop trying to use a hammer to fix a watch -- you are ignoring all the details of substance. A rational belief is one with non-null priors (e.g. children falling down stairs) and therefore it is reasonable to use this as an assertion. An irrational belief is one with one or more null priors (e.g. purple aliens stole my dog) and therefore cannot be reasonably used in an argument UNLESS you can prove that the priors are non-null (e.g. provide solid evidence that purple aliens even exist). These are the rules for "reason" in any rigorous sense. They do not change when one of the priors is "God", "Marxism", or any other arbitrary concept.
In your above statement, you've confused making a rational assertion with an irrational assertion. If the assertion is rational in the sense that it has all non-null priors, then it is reasonable for anyone to believe it. And even if they don't believe it, it is reasonable for you to use it in an argument as long as they accept that there are no null priors. This is "reason". If there is even one non-null prior, it is not reasonable for someone to believe it, and expecting that they should is unreasonable. Whether or not something happened is immaterial to whether or not it is rational for any one else to believe you. I could tell everyone that I saw my truck levitationg in my garage, and maybe I really did, but that does not constitute a reasonable assertion to most people and the onus is on me to prove that such things are possible.