"Believers Are Stupid"
Let's get one thing out of the way first: it's true that IQ does correlate somewhat with religiosity. A 2008 study examined data from 137 countries to come up with the following graph comparing countries' average IQ to percentage of atheists:
There are a few points to note here, however. Despite the clear positive trend, a few countries on the far left rank higher in IQ than those on the far right, and a "best fit" line would appear to flatten out at around 20% unbelief. And see all those countries pressed up against the left margin? Those are mostly third world countries with low rates of education. As for the extremely high rates of belief in God, many sociologists see it as a coping mechanism to deal with their low quality of life.
It's not accurate to make the generalization that "religious people are stupid": the data shows that as a whole the religious are only slightly less intelligent (often for unrelated reasons), and the brightest believers (e.g. Francis Collins) are certainly just as smart as the brightest non-believers. In fact, I don't think religiosity relates directly to intelligence at all. Intelligent people can be religious because they compartmentalize—they don't apply their intelligence to their religion. Religion is in a psychological category all its own, one that's perceived as incompatible with skeptical inquiry. Many were raised to hold certain comforting beliefs, grew up in a culture that supports those beliefs, made friends with others who believe as they do. Often they've never been taught to question those core values—and if they do, greater intelligence can help them invent more elaborate explanations that allow them to continue believing.
"Believers Are Hateful"
The word "hateful" is tossed around a lot. Sometimes it's used accurately (toward the Westboro Baptist Church, for example), but the term is so powerful and intense that it can be tempting to apply it to one's opponents even when it's undeserved. Religious people in general certainly don't deserve to be described as "hateful"—nor even do many fundamentalists.
Growing up as a evangelical Christian, I didn't "hate" gay people. It was strange to me that people could think and behave in that way, and I considered their actions sinful. That's as far as it went, and I think the same can be said for most fundamentalists. To disapprove of one aspect of a person's identity and to be weirded out by their sexuality is not the same as hatred of that person. The old saying "love the sinner, hate the sin" may seem trite to nonbelievers, but it's a genuine sentiment that's just as valid as saying "love the believer, hate the belief." I think we should avoid devaluing the word "hateful" and reserve it for those who actually detest another human being.
"Believers Are Crazy"
It can also be tempting to say that religious people have a mental disorder. After all, they believe strange and outlandish things, often fervently and without any logical basis. The idea that one can communicate with an invisible person wherever one goes does bear a resemblance to schizophrenia.
But ultimately, they've merely had a particularly enticing set of false beliefs ingrained into their psyches from an early age. That's not enough to call religiosity a mental illness in any sense except as a provocative rhetorical device. That being said, there's certainly some gray area here. What about those who roll around on the ground speaking in tongues, or actually claim to see angels and hear God's voice audibly? At what point do enculturation, social pressure and self-deception become pathology? I'll leave that for the mental health professionals to decide.
"Believers Know They're Wrong"
This one pops up more rarely, but some people really do think that believers realize deep down that their beliefs are false. Even David Silverman, president of American Atheists, said on The O'Reilly Factor that "everybody knows religion's a scam."
It should really go without saying that this is absolutely not the case. Certainly, there are many people who harbor serious doubts but convince themselves to continue believing due to wishful thinking. But the majority of believers accept their respective doctrines without reservation. For many years, I was one of them. To suggest that religious people are atheists in denial is just as insulting as suggesting that the reverse is true of atheists (an idea that rears its head with frustrating regularity).
"Believers Can't Be Reasoned With"
This sentiment is often expressed in terms of a quote: "You can't reason someone out of a position they didn't reason themselves into." As Matt Dillahunty of The Atheist Experience puts it, this is absolute "bull."
Is it difficult? Sure. Rare? Relatively speaking, yes. But it happens. Millions of atheists were raised as believers, but reached their own conclusions after either investigating on their own or being convinced by others. Once again, I'm one of them. According to this quote, I don't exist.
Maybe I'm being pedantic. Maybe most people interpret this as a general pattern rather than a hard-and-fast rule. But on more than one occasion I've heard it suggested that arguing with religious people is pointless, because none of them ever change their position. The idea that the faithful are immune to reason can be a serious obstacle to helping humanity move away from religion. Believers deserve more than dismissal from the non-believing community. Many of them are intellectually honest people who are willing to change their minds when they find that they can't defend their views. And even those who continue to believe may gain a deeper and more nuanced understanding of their own doctrines. Putting our most deeply cherished convictions under a microscope is hard for everyone. We owe it to believers to be there to help.