Torture is horrific and never amusing.
http://www.youtube.com/watch?v=NHujwj6RBSM

Meh, as far as I'm concerned, droids in SW become persons when you've got to know them, but until that, they're more like toys.
Doubt anyone got misty-eyed over that "red one" getting asploded in ANH... that was more like "ah, some prop blew up".

C-3P0 didn't scream of pain when his arm got chopped off, and I'm pretty sure R2's "screams" were also just mere imitation and alarm signal.
So the torture scene came off as both kinda absurd and surreal to me - couldn't shake off the feeling that the fear, and pain, were all just "imitation" and not that real.

Maybe that's why I can laugh at it.