It's easy to make the mistake of thinking of this statement as controversial, especially in a time when science is knocked for its perceived evils. But think about it in simple terms, and in fact in terms of a sphere where the practical and moral improvements are not just obvious but coincident. This sphere is the conquest of disease. I have been reading a fantastic book recently - Frank von Hippel's "The Chemical Age". The title betrays the content. The book is actually an amazing journey through various diseases that literally ended civilizations and destroyed the lives of millions, the lifesaving drugs and other public health measures science devised to end them and the heroic efforts of dogged individuals ranging from Louis Pasteur to Ronald Ross who defeated these implacable foes through blood, sweat and tears, sometimes quite literally so; Ross, during his efforts to prove that the malarial parasite was spread through the mosquito, worked so hard day and night at his microscope that the hinges rusted because of his sweat, the eyepiece cracked and he almost lost his eyesight. Another brave and almost otherworldly soul, a University of Pennsylvania doctoral student named Stubbins Ffirth, injected blood, urine and saliva from yellow fever patients into his body to rule out direct patient to patient transmission. These were the heroic deeds of heroic men.
But look at what they accomplished. Diseases like yellow fever, malaria and typhus, killers whose death toll easily exceeds the lives taken by all the wars of the world combined, which were endemic and a fact of life in ever city and village, which were literal destroyers of armies and even civilizations and scourges of families whose children they took away, were tamed, drastically reduced in intensity and fatal reach and finally contained. They haven't disappeared from our planet, but we, at least those of us who live in most developing and developed countries, hardly even think of any of these maladies any more, let alone know someone who has died of them.
This is not just a practical triumph of science but a profoundly moral one. Think of all the men, women and children numbering in the millions whose lives were saved, extended and enriched because of the innovations of chemistry and medicine, who could love and help and be there for each other and enjoy the blessings of precious life which in earlier ages was cruelly snatched away from them on a regular basis. In all these cases the "practical" and "moral" impact of science is indistinguishable.
This same overlap between the practical and the moral exists in other spheres. The discovery of cheap distillation methods for hydrocarbons not only enabled electricity and transportation but kept people warm in cold climates and cool in hot ones. Better chemical treatment of textiles led to similar, insulating material that protected the vulnerable and the young. And of course, far and away, the methods of artificial selection and genetic engineering have literally led to the feeding and saving of millions in parts of the world like India and China. If this existential improvement to humanity's basic predicaments by science isn't moral, I don't know what is.
The same book, von Hippel's, raises a counterargument when it talks about chemical weapons which disfigured and maimed millions. And yet the numbers don't compare. As hideous as thalidomide, sarin, phosgene and DDT are, the lives they claimed pale in significance and numbers compared to the lives saved by antibiotics, pesticides, disinfectants and the Haber-Bosch process; antibiotics for instance brought down the death toll due to infection on the battlefield from 200% (Civil War) to less than 10% in World War 2. Simpler measures like hand-washing and better sanitation were also the fruits of scientific discovery, and heretics like Ignaz Semmelweis who contributed to these measures were often hounded and ostracized; Semmelweis met a terribly tragic end when he died from beatings and possibly a self-inflicted wound in a mental asylum.
For me the conclusion is obvious. Science can indeed be used for good and evil, but the good outweighs the evil by an infinite amount. This is a timely reminder that the greatest force for practical improvement discovered by humanity is also the most moral one.