Of course, it wasn't explicitely marked as Baron Harkonnen quote, just as a Dune quote, so I wonder how many people realized.

As a Dune fan, I feel compelled to point out that this shouldn't surprise one. Both from an in-universe and out-of-universe perspective, the Harkonnens are written as characters which have a grip on a lot of truth. The Atreides were little morally better than the Harkonnens, Herbert tells us (he describes the former as descended from the Soviets!), and the latter are quite effective, both practically and genetically. As one should expect, given that the bloodlines mixed very early on in the plot, and given that the Harkonnens resoundingly defeated the Atreides - even if we ignore their conquest of Dune and award the Atreides victory because Muad'dib eventually managed to become Emperor, the Atreides ideals have still been utterly compromised (as remarked many times) and Muad'dib forced into scenarios he wanted desperately to avoid. Some victory. The Bene Gesserit weren't wrong in thinking that a Harkonnen-Atreides cross would be superhuman, they were wrong about the other things.