What you believe may be helpful or harmful not so much as to whether it is true or not, but how it helps you to navigate the world. If natural selection is true, we form our beliefs in a way inherited from ancestors who formed beliefs which aided them to survive and reproduce. Possibly, false beliefs may profit those who believe them. For some jobs, objective assessment of truth matters in the job itself- doctor, forensic scientist, police officer- but they might be able to be truthful there, yet hold false beliefs which do not directly impact their work.
I place a high value on truth. Possibly, that inhibited my acting in my own interests. I wondered, “Am I transsexual?” I assessed that by my understanding of the concept of transsexual, what observers considered it entailed, but now believe it is in part socially constructed and the important matter is the desire to transition. How should I judge people who habitually deny the truth?
Yuval Noah Harari writes that fiction helps people. Peugeot as an entity, rather than as a group of people and physical assets, depends on belief. The “Good-will” of a company is based on belief in it as an entity. Religions help people trust strangers, and co-operate.
Traits come in a range of strengths. People are varied. So, just because your ancestors held their beliefs in a particular way, and had offspring, does not mean that you will. I have no children, and neither had my uncle, who only married late in life, or aunt, who never married, and died in her early forties. Some inherited trait may be holding us back. My sister has children.
People hold contradictory beliefs. A belief may be useful for some purposes, but not for others; so you might ignore it in contexts where it is harmful. For the creationist doctor, scientists are arrogant fools when they disprove Creationism, but believeable enough when they research medical treatment. Or at least his suspicions of scientists do not result in angry denunciation, when it relates to his job.
Creationism in Christians could draw the community together. The community values belief in this sibboleth, and because outsiders despise it they have an Out-group to define themselves against. They might collect arguments for their position, building community.
It affects their understanding of wider society. They observe that there is a large group of people whose profession is (they believe) to make illegitimate conclusions from sparse, contradictory evidence, but who assert those conclusions with a high degree of confidence and despise the Creationists. Believing that so many people would have a professional interest in asserting falsehood would decrease trust in wider society. But perhaps they would not work out the full implications, which would cause cognitive dissonance.
I have been wondering about this after a Creationist wrote, I have solar on my roof, and I drive an electric car. I take better care of the environment than most, and have a smaller carbon footprint than many… all it would take is one large volcano eruption to put us into a persistent Global winter. I can find no assertion of persistent global winter from volcanoes, though that was one result of the Chicxulub impact. The second largest eruption of the 20th century, in Mount Pinatubo, put gases and solids into the stratosphere only for three weeks, but sulfate aerosols persisted for 3-4 years. The troposphere generally cooled, but warmed in winter. So says NASA: I don’t know how trustworthy he finds them. They have to be careful of truth while engineering rockets, or the rockets would not work. In 1816 the Tambora eruption in Indonesia created a “Year without a Summer” in the US and Western Europe. That would have been observed, by Christians, so have a high degree of credibility, but the connection is made by scientists. That was the largest volcanic event for 1300 years.
His understanding of science is grievously affected by his creationism, which requires him to disbelieve scientific knowledge and distrust science as practised. He misunderstands about volcanoes. Yet he behaves morally, as if climate science were true.
It is clearly easier for a science denier in one field to be a denier in another. Creationists are more likely to be climate deniers.
Possibly I overvalue truth. Trust in climate science, and indeed the scientific account of the history of life on Earth and the development of the Universe, is part of my trust in wider society. It feels like seasickness when someone denies the clear truth, either a Creationist or a conspiracy theorist. I feel angry when someone I know asserts that Saggitarians have particular traits, Diana was assassinated, or the World Trade Center was demolished by explosives rather than planes. I feel I depend on being able to discern truth. I don’t, really. The world is a complex and confusing place, and weird things happen. Knowing the age of the Universe does not make it more controllable.