Without seeing part 1, I'm estimating that the intrinsic background needed to enjoy part 2 is a leap I can manage without a viewing. That being:
Ass -> Mouth -> Ass -> Mouth... and so forth, yah?Know why the girl at the front wouldn't eat the beans? Because you can lead a human centipede to water but you can't make it drink.
I deduced that it was shot in B&W because eventually the blood/fecal matter splays would be too difficult to orchestrate, somehow?
There's a scene 1:14 into the film where the protagonist (is that the proper term for him?) finally has his ass-to-mouth centipede assembled, and succeeds in making the 12 people shit into each others mouths (cath-arse-is?). And it makes him vomit.
Staple-gunning people's lips to other people's buttholes, snipping leg tendons, yanking out tonsils with pliers, crowbars to the head and other varied... let's call them "shenanigans of the wee-and-psychotic," are accompanied sans visceral reaction. But this guy's bete noire is poop?
Dude, everybody poops.
As evidence I could cite many movies worse than this. It's torture porn, expect it. You don't go to a Michael Bay film hopeing for some semblance of an original plot and witty repartee.