Maybe it is...
But there's a simply fact that I think such people overlook: there are good beliefs (dogmas?), and bad ones. Good beliefs have a demonstrable connection to the world we live in... they attempt to explain and/or model reality in a useful fashion that - for all we can tell - appears to reflect external reality. From such deductions we can usually plan our interactions with the world in a logical way: i.e. - we can reason that walking off a cliff is not going to end well; we can use our insights into fluids, gravity, friction and energy to build an airplane. We can also use the process to deduce behaviors that will make us happy (e.g. - forming congenial bonds with one another is more likely to lead to 'happiness' than starting a feud).
Bad beliefs on the other hand aren't grounded in demonstrable reality. They may appear to serve a useful purpose - and that in itself isn't "bad" for society or the individual. For instance, believing in Santa Claus doesn't necessarily harm children. However, a life-long belief in Santa is considered to be abnormal behavior. Why? It isn't harmful right?
Such a belief is not supported by evidence and isn't "rational" given what we know about the universe we inhabit. Sustaining such a belief indicates that the belief holder really doesn't have a grasp on the mapping between what he observes (day-to-day) and what is fanciful (i.e. - imagined and maybe pleasant, but not supported by observation or logical deduction). What does that mean? It means he is failing to apply the experience and input from his life and formulate it in a consistent way. None of us are have perfectly consistent world views. But the hallmark of a rational/sane person is that he tries to reconcile the two - using (again) reason and evidence based logic. Those who don't do this are most often labeled "insane".
Anyway, if this Santa-believing-behavior exhibits itself not only in a 'self-delusional' way -- but informs the persons public interaction we quickly discount this person from positions of authority in our society: e.g. - Imagine electing someone to public office who thought Elvis is alive and well...
Hence we arrive at the crux of my problem with religion -- it not only propagates "bad" ideas, it does so in a way that informs public policy and enters our public debate. That's fine, but when you try to call people who have such ideas 'irrational' or simply 'stupid' you get your hand slapped. Somehow bad ideas that have been around for a long while under the banner of "faith" have become protected. Sam Harris put it better than I:
Now, it just so happens that religion has more than its fair share of bad ideas. And it remains the only system of thought, where the process of maintaining bad ideas in perpetual immunity from criticism is considered a sacred act. This is the act of faith. And I remain convinced that religious faith is one of the most perverse misuses of intelligence we have ever devised. So we will, inevitably, continue to criticize religious thinking.This is the crux of my argument: religion has more than it share of bad ideas and we should openly criticize them -- esp when they are informing public policy.
Lets recount a few of these bad ideas:
1- Condom use is a sin - even in sub-Saharan Africa where HIV is rampant.
2- The Jews have a god-given right to a patch of land in the middle-east.
3- A ball of 150 or so undifferentiated cells in a petri dish is a Human being and its interests must be protected.
4- The Earth is about 6000 years old and god created all of the species that now inhabit it.
5- Slavery is ordained by god.
6- Drugs (certain ones) are evil and must be banned.
All these religiously motivated ideas impact each of us to a degree: some more than others. None of them are good ideas. None of them are supported by ANY evidence what-so-ever. Yet many many people in our society (and elsewhere) use these "facts" to inform their decisions -- including a LARGE percentage of our elected leaders.
In rebuttal some say that religion and faith can also be used to refute these very positions. That is true: when you start with arbitrary belief you can bend it to whatever purpose you desire. Besides that being the problem, there is a simpler way: a straightforward analysis (where you imagine a loved one or family member in the slaves shoes) yields the conclusion that slavery is bad. Of course, some proffer other irrational and unsubstantiated beliefs (like black people are not really people) to justify their position... but again, asking for evidence and reasons for a conclusion is always the answer to such arguments.
It boils down to demanding intellectual honesty from people. How can you argue with that?