The problem with the 'torture' of Gollum is that it puts Faramir and his men in a bad light. Remember, in FotR, we hear Gollum's shrieks as he endures an interrogation in the dungeons of Sauron. Great company for Faramir to be in, to be sure. Now, I can see PJ thinking that if he were to show Gollum being beaten that it would be clear to all why he turns back to the dark side. This is typical of moreMoreMORE PJ as it's not enough for Gollum to feel betrayed when Frodo leads him into the hands of Faramir's men. No, we need more and then some to make sure the message 'hits' home. It doesn't work for me as I feel sorry for Gollum, and again, it's hard to watch this small frail wretched creature being abused.
Sure it's just smoke and mirrors; Andy Serkis and CG, but think about it. When Boromir lay dying, Sean Bean was in no mortal (or spiritual) peril, and when the scene was finished, he would get up and go back to his trailer, yet I was moved to (almost) tears as Boromir spoke his last words to his new-found brother. Also got a surge of something when the Elves appeared at Helm's Deep - actors/models all, and not, by the book, even supposed to be there. And, of course, when Dread Pirate Peter catches one of Legolas's arrows, don't you just choke up...hmmm, okay, so that might not be a good example.
PJ and WETA painstakingly strove to make us believe that Gollum is real. In that, they were very successful, and that's why I see not CG, or an actor, but a underdog being bullied and beaten, all so that (I assume) I can easily understand why he will turn against his master.
Just in case I would forget, Faramir abuses Gollum once again at the end of TTT before Gollum follows Sam and Frodo in the old sewers of Osgiliath.
Shelob and the oliphaunts were CG, but, seemingly, we have mixed emotions about these creatures. My guess is that persons may warm a bit more to the Middle Earth proto-elephants as they are mammals, have real world cousins that, for the most part, are seen and presented in a good light and that the behemoths most likely did not choose to be horse stompers but were enslaved and forced into servitude. Shelob, on the other side, is a large bug, has deadly real world cousins (but most aren't) which are shown more infamously (think Halloween, were one finds more scary spider decorations than eerie elephants) and acts on her own - she hunts those that pass through her lair.
My children would be more afraid of Shelob (like PJ) than the oliphaunts - though my one daughter is more and more like Wednesday Addams every day, and has taken to playing with small bugs.
Anyway...