ignorance, isolation......deprivation....lack of education...radical belief systems.....tradition and misinformation. propaganda.
fear, ignorance, and many times- influence from your upbringing.
Undesirable acts carried out by the same race repeatedly.
Common sense is the collection of prejudices acquired by age eighteen. & It is harder to crack a prejudice than an atom. -Albert Einstein
Bigotry and prejudices are, like Puck said, mainly from fear. But they are from society as well. It's caused by unhappiness within ourselves and community.
stupidity and paranoia. A dangerous combo.
AND IGNORANCE, OR FEAR
Dang it! puck beat me. :p