Why are people so ignorant?

As we have been watching, "The Protocols of Zion," I was kinda surprised how idiotic some people can be. I found it so funny how people love to believe everything they are told, or what they hear or see without having proof. Especially when its about judging and making false judgement and assumptions about specific groups of people. I had no idea that after the 9/11 tragedy, people turned to Jewish to blame for. One thing humans are really good to do when something tragedy  occurs is turn to someone or others to blame. Not fully knowing the facts or who/what/why things happen. During the video it was humiliating watching knowledgeable people speak so badly about Jewish people, contradicting themselves making no sense. I don't fully understand why people have to be so knowledgeable and gullible. I truly believe that "The Protocols of Zion," was written so that people could have "proof" to support their "ideas" of Jewish people being the most evil people alive.