How does that question even make sense? By definition, the spread is a tax investors --- including small investors --- pay to buy or sell a holding. In what way could they possibly benefit from wider spreads?

Regarding Flash Boys: I don't know of a single person who works in trading who has stuck up for that book. I strongly recommend "Flash Boys: Not So Fast", which debunks it but is also much more interesting from a technical perspective than Lewis's book.