Rheingold includes a large swath of Nicholas Carr's quotes on this page and next, which I'm not sure is helping his larger point. I happen to agree with some of Carr's arguments including this one. While I do believe its overstated, I think that his point that with there being so much content just 'out there' on the Internet, its hard to wade through the sludge for correct information, particularly if you don't have well-developed digital literacy skills.
This is another area where media stratification comes into play. The Internet has exacerbated the issue of confirmation bias in current events, because of its democratized nature. Everyone can publish content on the web, and because of that then anyone can find a source that aligns perfectly with their beliefs and biases, whether they're grounded in fact or not.
This is a huge contributor to the rise of the alt-right over the past year and a half. The publication of conspiracy theories, of abhorrent racist content, of confederate rage that make up alt-right circles on the Internet was a major news story during America's most recent election. Carr's point about the Internet forcing us to become 'hunters and gatherers in the electronic data forest' means that people naturally flock to sources that confirm biases they already hold.