Professor Daniel Dennett argues it is:I don't believe that the human animal can function without faith. Faith is a shorthand for a hunch that things will work out all right, even if you can't see how it will happen at the moment. But the problem is that, while faith is essential to supporting right action, religious faith can also inform us to perform patently wrong action. Some of those actions merely make life the poorer: When you shun a neighbor because he believes the wrong thing and is therefore going to your version of Hell, your neighborhood is the poorer for it. When you elect officials on your school board because they promise to teach things as science that have no scientific basis, you intellectually hobble your town's children and deny them some of the most useful tools that modern society has to offer for making their lives better.If religion isn't the greatest threat to rationality and scientific progress, what is? Perhaps alcohol, or television, or addictive video games. But although each of these scourges - mixed blessings, in fact - has the power to overwhelm our best judgment and cloud our critical faculties, religion has a feature of that none of them can boast: it doesn't just disable, it honours the disability. People are revered for their capacity to live in a dream world, to shield their minds from factual knowledge and make the major decisions of their lives by consulting voices in their heads that they call forth by rituals designed to intoxicate them.While Lord Winston argues it isn't:The problem is that scientists now too frequently believe we have the answers to these questions, and hence the mysteries of life. But, oddly, the more we use science to explore nature, the more we find things we do not understand and cannot explain. In reality, both religion and science are expressions of man's uncertainty. Perhaps the paradox is that certainty, whether it be in science or religion, is dangerous. The danger of Dennett's relatively gentle brand of certainty is that it increases polarisation in our society. With inflexible positions on both sides, certainty surely is the biggest threat to rationality, and to science.
And of course some faith-based actions kill people: When your religion demands that you stone somebody for adultery, or kill them for apostasy, or approve of others assassinating blasphemers, or make war on another country because you deem their brand of belief to be evil, you're doing more than simply making life poorer; you're degrading civilization itself.
(Note the fine line here: We act on things that were originally faith-based all the time. Our legal code is riddled with strictures that started out as religious but which have proven to be recipes for good civilization. There may be no moral reason why murder is illegal but there are certainly pragmatic reasons why social violence needs to be prevented. It's harder to make a case for laws that forbid drugs, gambling, prostitution, and obscenity but some of those laws make for better civilizations, too. I'm just not sure which ones are which.)
If religion were strictly the province of the unknowable, that would be one thing. The problem is that religion makes certain assertions that are simply untrue. Your answer to the question, "Does God exist, does he watch over me, judge my actions, and grant me eternal life if I'm good?" is fairly harmless. Your answer to the question, "What does God want me to do to defend him and promote his revelation to me?" is not harmless.
Similarly, if science were strictly the province of the knowable, the limits of its use would be clear. But scientists have hunches, too. Some of the hunches get passed off--erroneously--as theory when they are no more than hypothesis. Science and epistemology have good answers for the boundaries between the knowable and the unknowable. Unfortunately, those boundaries are often ignored by scientists with an agenda. Within the scientific community, that usually results in peer-review that corrects the error. But when scientists assert that something is true to laypeople when it is merely conjecture, they're committing exactly the same evil that a religious person does when he imposes his beliefs on another. That sort of arrogance is incredibly dangerous, especially since so much of science is intended to produce actionable truth.
So the scientist and the religionist ultimately have exactly the same responsibility. They can believe whatever they want. But they have a duty to distinguish fact from belief and only act on the former. It's pointless and destructive to deny the need for the latter, but it ultimately can't inform our actions.