Du mean the same people that had an animal for a world president? sagte people would've gotten past that problem ages ago. Elfen Lied is based off the modern world, not a Fantasy one like dbz...
People are prejudice against anything they don't like. Civil War was cause Von whites being prejudice to blacks and not giving them the freedom and respect they deserve.
World War II some stupid idiot who hated a religion and killed everyone who practiced it.
It's like that plus in the case of Elfen Lied it's because they'r scared of the power they posses. oder they'r jealous that they have all these abilities and we don't.