How about this one, from Plessy v. Ferguson: "Legislation is powerless to eradicate racial instincts, or to abolish distinctions based upon physical differences, and the attempt to do so can only result in accentuating the difficulties of the present situation." Here you have three incorrect, and quite damaging, "scientific" propositions: (1) That there are "racial instincts"; (2) That "physical differences" account for policies like segregation; (3) and that overturning a law that requires segregation will somehow inevitably result in exacerbated racial tensions. Note that the latter view was consistent with the view of many "Progressive" southerners of the late 19th century, who believed that by separating the races, government-ordered segregation would reduce racial tensions and ultimately benefit African Americans. Of course they were wrong, and the Supreme Court was even more wrong to make this into a scientific proposition. The Court could have, for example, simply state "some people believe this, so we'll defer to legislative judgment." The outcome would have been just as bad, but the Court would not have been endorsing a fallacious "scientific" proposition.