imho there is only one real reason behind the hate and has nothing to do with how difficult lfr is, peoples hate it because it completely drained guild recruiting pool and i'm not talking about high end heroic/mythic guilds, those i'm talking about were friends&family guilds those who back in wrath run 10man/25man(with pug members) normal mode.
Nowadays only those really interested enter a guild, being it for the challenge or for the extra reward the others just run lfr that killed a plethora of guilds who had survived only thanks to peoples being forced to commit to one; there is a salty bunch of ex GM, ex RL and ex Officers who don't have the ability to run a decent guild who hate lfr.