Sometimes we hold misguided beliefs about the world around us due to lapses in judgement. Most people aren't to blame for this because they aren't aware of certain neurological lapses known as cognitive biases. Recently, there has been a lot of anti-immigration rhetoric all around the world that cites terrorist threats as a main selling point. It's easy to fall for this rhetoric because of a cognitive bias known as the availability heuristic. Essentially, our brains tend to take the most recent piece of information about a certain topic and believe that it is the most important regarding to the topic at hand. When observing terrorist attacks on the news, our brains tend to over inflate the prevalence of such events around the world. Once politicians or other influential individuals begin linking terrorism to immigration, we are easily influenced to rally against immigration.
Now, this is not to say that politicians are always trying to manipulate us, just that it's important to stay grounded in reason, and not let irrational fear override our decision making process.