The answer is that the most important facts noted by science began as opinions and acquired certainty over many repeated trials over many years. At some point it was concluded that neither matter nor energy can be created nor destroyed. It was decided that the certainty of the fact was comparable to the "law" of gravity and so it is called a "law" of thermodynamics.
The opinion that life cannot arise from dead matter without an intelligent designer has sufficient repeated trials over sufficient years to quaify as the "law" of intelligent design, with every bit as much certainty of fact as the "law" of gravity. A problem remains having this recognized.
The problem is historical. There was a time when life was thought to exist in extremely simple forms such as might be randomly assembled. The euglena at 150 times magnification appears to be a little drop of green jelly, but it can swim and will seek the sunny side of its container of water. In those primitive times of low power microscopes "science" developed a "bias" that no intelligent designer was necessary. It is that bias, not true science, that prevents the law of intelligent design being taught in American public schools.
As with some other laws in science things developed slowly. One landmark occured with the discovery, as microscope technology improved, of the chromosome and the growing realization that things were far more complicated than Mendel or Darwin had anticipated. These days we have highly detailed maps of several complex processes necessary for life, even that of the euglena.
The overwhelming public opinion, still based on an early mistake by science, is still that no intelligent designer is required. It is a very popular opinion because it seems to give people more control of things. They like to govern things and that can mean being coercive at times. If they had to recognize the existence of an intelligent designer they would have to minimize their coercion.
Publilius Syrus
The decision in Kitzmiller v. Dover was based on that public opinion, not the current science. The principle arguments in the case were made and heard by people who likely hadn't seen a biology book in thirty years. When they were in college the Miller-Urey experiment had revived for a while the dying notion that random assembly of life was possible. It is impossible with a modern college biology textbook, showing the vast compexity of even the simplest living things, to doubt the law of intelligent design any more than the law of gravity.
People who cherish the government of the United States as it was founded tend to like the idea of an intelligent designer because they believe government should minimize coercion. People who really believe in God, understandably, tend to like the idea of an intelligent designer. Intelligent design should not be excluded from public schools on those grounds as that would be an ad hominem argument.
How did so many people who aren't scientists come to believe that they are?
In the twentieth century science changed the way people live far more than in any previous hundred year span. Developing ideas born just before the turn of the 20th century; radios and automobiles, and others, powered human flight and television, scientific discoveries, inventions and advancements in communications and transportation revolutionized the way people live. The discovery of nuclear power has made mankind responsible for the earth on a scale never dreamed before, and the journey into space and placement of communication satellites has made the world "smaller" with nearly instantaneous communication possible to any part of it.
All these discoveries have given mankind and democracy a confidence in its own powers and abilities.
It was the year 1973, about four years after the first manned moon landing, that the American Psychological Association removed homosexuaity from its list of named psychological disorders. Some like to think that means it is a scientific "fact" that homosexuality is not a mental disorder. An attempt to present the real science is made in these articles.
Such laxity of marriage laws that could compare the union of biological parents to that of homosexuals is widespread, but might be worse for people in movies and televison. Most people can't flit in and out of marriages like coffee shops. This might explain why so many on television seem to believe homosexuality is fine.