I don't see how understanding, acceptance, and love follow from rationality.

They do not follow from it, they are necessary to it.

• You need to relate well to yourself and others (love) in order to actually accomplish anything worthwhile without then turning around and sabotaging it.
• If you discover something, you need to accept what is actually going on in order to come to understand it, and understand it in order to apply it.

Are you saying that rationalism is a "philosophy of life", even leaving the soundness aside for a minute?

No. But a story that is trying to have broad appeal needs these things, whether it's a story about rationality or about watching paint dry. A story conveys a sense of life.

The parent comment said: "You need a good story. That's all. A good story."

That's not vague. That's wrong.

That depends on what you think 'good' is supposed to imply there. If 'convincing' is the intended connotation, then yeah, wrong. If 'consistent' is the intended connotation, that is not obviously wrong, People need stories to help them get stuff done, even though stories are overall pretty terrible.

Science, for example, has methods, but overall science is a story about how to get accurate data and interpret it accurately in spite of our human failings. The way that the elements of that story were obtained does not make it any less of a story. History itself is a story, no matter how accurate you get, it remains a narrative rather than a fact. Reality exists, but all descriptions of it are stories; there are no facts found in stories; Facts are made of reality, not of words.