Most Helpful Girl
Many people in N. America don’t come across Muslims very often. When the only information about Muslims the average individual comes across typically involves a bombing in France, or ISIS decapitating a US citizen in Syria, it is hard to not form preconceptions against Muslims in general.
When more of these similar news pop up, the viewer’s preconceptions further strengthens via confirmation bias. That is not to say that this action is right, it isn’t. However, it is simply a heuristic (mental shortcut), coined as ‘schema’ that is generally pretty useful when it comes to daily life. Not so useful when it comes to grouping people though, because that is how stereotypes are formed.1
Most Helpful Guy
Thanks to a shortcut human brains take called "Out-group Homogeneity Bias". Basically, it's the notion that people in other groups we don't belong in are more similar to each other than people within our own groups.
For example: I would consider myself a nerd, a group of people who are intensely infatuated with video games and the fiction/fantasy genre. Being a nerd, however, is a bunch of different things. There are gamers who are speed runners, casuals, or achievement hunters. There are Kirk Trekkies and Picard Trekkies, and so on. To confuse any of those groups with the others is not something you want to do in front of them, because that would be like calling a Catholic a Pentacostal (similar, but with drastic differences).
To the outside observer, however, we are all just nerds. Let's take a sports jock, for instance. To him, nerds are just socially awkward individuals who live in fantasy worlds. In his world, the world of a sports jock, there are a bunch of different subgroups- there is American Football, Soccer, Baseball, Basketball, Rugby, Hockey, etc. To confuse any of those sports, their fans, or their players, would be an egregious mistake to someone who is a part of jock culture. On the outside, say, to a nerd, jocks are all just dumb meatheads.
Out-group Homogeneity Bias necessarily comes from a lack of information. Because all that nerds who aren't involved in sports ever see jocks doing is being meatheads, they make the assumption that sports fans are all that way, which is not true. Just in the same note, jocks see nerds as socially awkward individuals, which I can also tell you is just not true.
Knowing this, we apply it to your original question, "Why do people hate Muslims?" The answer is simple: Out-group Homogeneity Bias. The only place many in the West see Muslims is on the news channels, and it almost always is about how they are terrorists in some attack somewhere in the world. They only see them as the enemy. They don't know that that is a very small portion of Muslims. They make the assumption that what they've seen a few people do is true of all of the people who are Muslim.
Is it right? No, it's not. We need to be more aware of others today than ever. The problem is is that Muslims need to be cast in more roles than just "Terrorist". The people of that faith need to be shown as more than religious fanatics. Otherwise, all people will ever see are terrorists. And who can blame them for hating terrorists?0