It sounds like there were two objections:
1. OMG, this site is pirating my content! 2. I didn't want people to lend to anyone, just their friends and family
Case #1 is clearly an issue of authors being misinformed or technologically unsophisticated.
Case #2 is that authors probably thought that they were buying into a particular scenario, but the technology did not actually serve that scenario. The scenario I'm guessing the second camp thought they were buying into was one where lending would actually not be widespread --- where one would have to personally know someone in order to read a book without purchasing. It didn't limit who could be lent to by forcing users to declare "friends and family". I'm guessing that authors felt that LendInk was increasing the amount of lends actually happening above what would have happened had LendInk not been present.
Note: I'm not passing judgement on LendInk. Just that I don't think many people are able to make the technical distinctions that many HN readers or readers of tech sites are able to make.