I know for a fact that there are much worse things than chopped liver. How did chopped liver earn its reputation for implying insignificance?
How about: So what am I, haggis? So what am I, blood sausage?
I, personally, love chopped liver. So, Sly, if you were chopped liver to me, you’d be special indeed! 
This is a WAG, but I don’t think the implication of the phrase is to indicate that the person is worthless. Chopped liver is a very simple food, with almost no spices or other ingredients. I think what the phrase means is, “so what am I, something ordinary?”
On the other hand, being “toast” has to do with being utterly annihilated, and that makes no sense to me, either.
American English is a peculiar language.
I think “chopped liver” has distinctly negative connotations for many people. Far beyond the realm of ordinary foods lies that quivering pile of occult-blood-in-your-stool colored dead animal organ. Yugg.
mmm chopped liver with alittle bacon and sauteed onions!
To deal with men by force is as impractical as to deal with nature by persuasion.
CK–you’re confusing the noun “toast” with the verb “toast”. When someone is “toasted”, they are metaphorically burned to destruction, not metaphorically made into a breakfast food.
Nickrz–you’re forgetting that the “chopped liver” phrase is most closely associated with Jews. Since chopped liver is a pretty popular Jewish food (isn’t it eaten at Passovoer–someone help me here), they wouldn’t view it with the same loathing and disgust you do.
Of course, as a Gentile, I must point out that I think chopped liver is pretty yummy.
Growing up in Catholic schools most of my life, liver was usually the Wednesday or Thursday “Mystery Meat” served in the lunch room. (Now Adam Sandler’s “Lunch Lady” song has suddenly started up in my head). I can’t stand the smell of it to this day.
“…send lawyers, guns, and money…”
Warren ZevonWhy on earth did we drag Jews into this?
I said “many people.” Also note, I did not necessarily include myself in that sphere. I happen to like liver.
Dex, ever had my wife’s toast? OWWWWWWW! when did you get home honey?
Signitorily yours, Mr John
" Pardon me while I have a strange interlude."-Marx
“…”-Marx
If chopped liver is pate de fois gras, then the “chopped liver” asignee is special indeed.
If chopped liver is braunschweiger, then it's a pretty good sandwich spread. But OY VEY! The cholesterol!!!
“There will always be somebody who’s never read a book who’ll know twice what you know.” - D.Duchovny
Chopped liver is always a side dish, never the main course (chopped liver is so rich that if it were the main course, the diner would probably drop dead halfway through the meal).
To say, “What am I, chopped liver?”, then, is to say, “What am I, an unimportant matter away from the main concern?”
“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”
Hey, I like blood sausage
or should I say
Ich liebe blutwurst!
“Nuts!”
Gen A.C. McAuliffe
“The general’s nuts.”
unknown 101st AB grunt
I don’t think the idea is that chopped liver is disgusting, I think the idea is that it’s hard to think of anything less important in the world than chopped liver. It doesn’t have the substance to be a main course, it doesn’t really work as an appetizer, being meat, it isn’t usually served as a side dish and it’s certainly not a desert. That’s why the phrase is said when someone is ignored.
On a side note, my grandmother used to make what she called ‘vegetarian chopped liver’ which was made of things like eggs, walnuts and green beans. It’s delicious. Doesn’t taste like liver though.