> Rationally I should have multiple children, as my only legacy is my name.
I would say that any view that includes a concept such as "legacy" is already highly irrational... there's nothing rational about having a world view that you do not call into doubt.
At the end of the day, you'll just gravitate towards a worldview that's the easiest to support. That's what tends to happen to people since cognitive dissonance hurts. There's nothing rational whatsoever in this entire process and it is the very start of the problem, you can't ignore it.
The whole problem with "rational" is that it's a poor term that got appropriated to describe behaviors that are not actually rational.
"Rational" is mostly a shorthand for "logically derived", which is only one rather shallow facet of processing, and, not all that surprisingly, can lead to rather irrational behaviors, like the ones the person you're responding to is referencing. It often leads to nihilism, amoral philosophies, and other things that play right into the worst parts of game theory. Because this is what we naturally do if we turn off other processing. We have all the other processing for a reason.
Emotions, intuition, and experience are all very important. Pure logic cannot replace them, it is simply too slow, and there's simply not enough information. The reason a lot of us are really annoyed with rationalists is because they're walking around saying all those things don't matter.