I think its not the problem that the game might 'acknowledge' it in a way, just that some of us think that the concept itself is too dark for what appeared in King's Quest in general. It's not the kind of thing Roberta did in her games, except for maybe if you take Phantasmagoria into consideration (and she received criticism for that game for that very reason, interestingly enough)...
The same can be said for some elements in TSL, you have added quite a few dark things, even some ideas such as parental abuse and perhaps going as far as 'mind raping' (Manannan to Valanice, or Shadrack to Rosella). Yes, your game does a decent job of 'acknowledging' how disturbing such concepts are... But do such concepts fit into what KQ is known for, or have appeared in previous KQ games? Many fans don't believe so... others might... I guess to each their own...
But I fall under the crowd that thinks some of this subject matter is too dark for KQ, and better fits into the realms of Gabriel Knight or other psychological thrillers.
Even official companies can do things to a series that don't always pass judgement by all the fans.
Lucasfilm received some criticism for a scene that appeared in the Radio Show version of Stars Wars films, in which Vader tortures Leia... Some critics likened it to rape, incest or molestation, because the way Vader was showing enjoyment over it, and acting as if he is her 'father' Bail Organa (while Leia screamed and moaned throughout the entire scene), and in hindsight they knew she was really his daughter... They felt that while Star Wars has scenes of dramatic darkness, that overall the original trilogy never got as dark or disturbing as that scene, since it was designed for children to watch! They felt that such a scene in the radio show, far more 'porno'graphic in nature, was disturbingly not for children or the squeemish!
http://www.youtube.com/watch?v=itBXNe6mEnY