How does that work if the character isn't a white middle-class American male? Harsh perhaps, but the point being that Bova's technique only works if those reactions, etc., can be interpreted by the reader - which means the reader must share a whole raft of assumptions, prejudices and cultural references with the character. If you have a completely invented society, and the POV character is a member of that society, then it gets much trickier. It has been done... and I'm trying to think of examples... Courtship Rite by Donald Kingsbury? Nope, I'm stuck...
I didn't mean cultural reactions of someone from our culture reacting to their culture. I meant cultural reactions of someone living within the culture. If everyone is required to wear blue hats or they're put to death and the character sees someone with a red hat, he'll have a cultural reaction towards the person not wearing the blue hat. Even when the red hat wearer is executed, he'll wonder at the bravery of the red hat wearer. It is a stupid example but the best I can think of at 6 in the morning.
It isn't a required thing to have an everyman do all the reacting to the invented society. A good, concise third person limited narrative in which the author thoroughly gets inside the POV character's head will give all the necessary cultural references with how he handles the situations. You'll infer to the reader what the norms are, the taboos are, and what the character expects. With the example above, what made the red hat wearer risk death just to be different? Why are they all wearing blue hats? What events led to the blue hat law? All those questions arise because of the situation, and then the talented author uses one of the best SF narrative techniques, abeyance. The reader holds those questions in abeyance until situations arise where the answers are revealed.
A lot of folks never realize that readers wondering why things happen a certain way, or why the character feels a certain way, can be used as another narrative hook. In these cases the world building you did is used as a plot device and hooks the reader; they're dying to know about the red hat wearer as the POV character begins to question the notion of wearing blue hats. Since no info dump has occured, the reader gets the information trickled in where it is relevant and all the hard work you've put into building the blue hat wearing world pays off with the world being intrinsic to the situation and not only is the reader hooked on wanting to know more about the world (instead of having it dumped on him) but also cheering on the POV character as he discovers the events that led to the brave martyrdom of the red hat wearer.
So Bova's point: After constructing a character and a situation you can do the necessary world building to discover more about the character and situation. By doing it in that order before the writing process begins you not only create an internally consistent world but also make sure that the world you built is completely necessary to the plot, not only necessary but inseperably intwined with the plot.
So, another example of why world building isn't pointless and Harrison is wroooong, according to me and Ben Bova. But hey, Ben Bova is quite the person to disagree with as he is a very popular SF author.