What is the basis of all prejudice?

The old maxim is that "ignorance is at the basis of all prejudice." [1] (I do not know who originally said that)

Although the above is probably the answer you wanted, note that others have stated...

"Rigidity is the basis of all prejudice" : quote from Wayne W. Dyer in the book "Your Erroneous Zones: Step-by-Step Advice for Escaping". [2]

On one website, which was An Analysis of To Kill a Mockingbird, it stated: "The first character to be judged swiftly and wrongly is the Finch's neighbor Boo Radley. Boo is introduced as a hermit that lives shut up in his house, completely isolated from the outside world. Dill, Jem, and Scout spend most of their free time either ridiculing Boo or trying to lure him out of his house. By using the children's innocent fear of the unknown, Harper Lee succeeds in demonstrating the basis of all prejudice. In the end, the Finch's bizarre neighbor becomes a hero and saves the children from almost certain death. While the children imagined and concluded Boo was a monster of some sort, he ends up saving the children of whom he knows almost nothing about. This part also brings about a decision where abiding by the law would be an injustice.". [3]

Patricia Reader on a comment board while reviewing The Forgotten Daughter, stated:

"Another thing to think about, while reading this book -- our prejudices. Against those who are illegitmate, who are "wage-slave, working-class" people, who are gay, who are Black, or Jewish, or women, or handicapped...and who belong to any other "minority" group". How much do things things really matter -- and do they, or should they, really matter at all? The basis of all prejudice, really, is a game of "one-upmanship", after all. One can be, say, handicapped and Black -- but "at least" not poor, or illegitmate! This is a form of prejudice, like any other. Chloe in this book is both poor, (and less than poor -- "owned" as a piece of property!), and also illegitimate...but what of it? She is as sterling a fictional character as ever was written! She suffers much in this book...but is also resourceful, intelligent -- and also learns to love and be loved, and to let go of (false) feelings she has held all her life! (Jeffrey Daumer, the real-life human cannibal, was quite legitimately born, as was Adolf Hitler! Give me the illegitmate, fictional Chloe, any time!) " [4]