Well that's an interesting theory. However, on reading it, my leading hypotheses are that people who express such disbelief in the possibility of their being selfish, either lack self-insight, or are lying. Your theory I would give a subjective probability rather lower than these.

Of course, this might be my lack of insight into the aspie mind. But self-interest is highly evolutionarily favourable, and is built into our brains from very early in our evolutionary history - from the first organisms that had brains.