You would be wrong. That would be irrational. I will for the moment assume you did not intentionally obfuscate the obvious: The pursuit of his own rational self-interest and of his own happiness is the highest moral purpose of his life.
Ayn Rand never said that is what all men do (most do not), or that they could claim to do this, (without actually doing it) and it would still count as rational self-interest. That's pretty simple. How could you miss this?
Hank