I don't really agree with the OP, but that's not true. It's a quote which discusses people as a category in the abstract, which is to say it discusses the idea of people and their behavior. As much as I'd like to dunk on the quote like this, it is consistent :)

My interpretation of the quote has always been that discussing people means something along the lines of gossip, i.e. specific people. That being said I think there's a clear difference between simple gossip and critical discussion of others, which can be very intellectually elevated.