2 quoted lines
Jerry Friedman: If the people on Blue and Green were non-parasitic, the inhumi couldn't parasitize them, and if the people were honest, the inhumi would be honest and couldn't deceive them. Then inhumi preying on people would stop, and the next generation would have only animal intelligence, at which point people could wipe them out (or keep a few in parks and zoos).
nate jarvis: If everyone on Earth stops having sex or doing needle drugs for what? a year? then we all go and get AIDS tests, then AIDS is cured. THAT sounds more likely than everyone being nice to one another to wipe out vampire-like monsters they'd rather lynch. Horn seems to to feel if he revealed the secret it would spell trouble for the inhumi as well.
My own thinking is in line with nates, but I have to admit that Jerry's thinking is congruent with Wolfe's quote in the Gevers interview. Perhaps we are just supposed to accept it at face value. (urg..but I just...can't...do....that)