In case you don’t know, projection in the Freudian sense, is when a person subconsciously denies their own attributes and then ascribes them to other people. For example, a person may be very racist against black people and claim that black people harbor a great racism against white people. The point here is not whether or not racism exists in whites or blacks (I’ve read that subconscious racism exists in all of us), but rather that the reason why the “projector” says the other group is racist is because they feel guilt for their own racism.
This is something that happens often with religious people. There is the constant claim that non-believers are immoral; however, there are plenty of instances of immorality due to religious belief. Hatred of other groups, slavery, and child abuse are all immoral behaviors that are supported by the bible. As a result, any sufficiently intelligent Christian cannot hold the two beliefs that their religion is wholly moral and that these examples of immorality exist within their belief system without some psychological reaction. The reaction is generally projection.
There are other examples. What is one extremely taboo subject among most religions? In a word, sex. The question of why this originally entered the worldviews of believers — that is, why the holy texts assert that sex is bad — is a more complicated question than I am willing to get into here. What I’m referring to, is why is there a visceral reaction among the religious whenever the topic of sex comes up? It is because, simply, everyone has an interest in sex. The repression of this impulse causes the need for projection. The actual subconscious thinking process is something like this: “I enjoy sex. No, I shouldn’t believe that because my holy book says it’s bad. Ok, I’ll try to stop enjoying sex. Hey, that girl over there is dressing provocatively and flirting with a man! Why is she allowed to think about sex and I’m not? She’s a slut! She always thinks about sex while I, as a pure believer, never think about sex!” The result is what we see in religious communities the world round. Pre-marital sex prohibition, extra-marital sex legal prohibition (by stoning in Islam), homosexual sex prohibition, non-standard sex (that is, anything but missionary position) prohibition, sexual dress prohibition, and so on. These are all forms of projections or, to put it another way, envy. This is not a mentally healthy way to live one’s life.
Once you have this understanding of projection, the behavior (and motivation for such behavior) of many religious people becomes somewhat predictable.