I wouldn't say that they are identical but I defiantly see the resemblances which are actually a bit more subjective than 'some food getting knifed once in this video' besides the editing, pace of the sequence, composition, music and even colors the subject matter posses similarities i.e. the everyday activities that take on homicidal (not limited to) imagery, in the American Psycho scene we are showed the preparation of a meal which involves cuts and slices and what looks like blood etc which all obviously will have a different affect on a first time viewer as in most respects they will have no idea of the complexity of the character they are about to experience in that film, however it achieves its goal which is to create that dark, compulsive, quirky and even mischievous murderous overtone which is so prominent throughout the movie I don't blame them for accentuating that in the opening credits. With Dexter we almost see an expansion of this same undertone as its a lot more important to the psychology of the main character and our ability to empathize with him, we see his everyday 'ritual' and how the same grace and etiquette is parallel with other 'rituals' its goes far to reinforce the fact that this man is a killer and that in reality he cannot escape that, by drawing the similarities between the everyday ritual and Dexter's methods and techniques we are given a hint as to Dexter's outlook on the world and just how prominent his true self is, as if he is so obviously insane and dangerous that you can't tell he is.
In short they both were used for identical reasons, basically any opening sequence should create an overtone which the movie/show adopts and develops into important an theme, motif, symbol or as I have explained even the psychology of a character.

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"You are so right. I even looked up sociopath to double check. I think that maybe the cause of his problems were due to trauma and not someone he was born with so maybe there's hope. I hope they explain it more this season because no matter how many times he says he has no emotions, he clearly does. "

I think about this everytime they show him having some sort of emotion. The sociopathy was caused by extreme mental trauma, but the question is, once the brain is wired that way, can you change it? They have been studying the minds of serial killers for years, if they could change them, don't you think they would? I thought that maybe once Dexter remembered what happened to him as a child (with Brian/Rudy's help, that is) it brought a rush of emotions in. What I still don't understand is why didn't they start putting Dexter in therapy as soon as he was old enough to go through it? Harry hid it from everybody and basically trained him to kill bad people. Some people think that Harry did the right thing, others, not so much.

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