Answer: Plessy v. Ferguson
A dissenting opinion in a case is one that goes against the majority opinion.
In this case, the excerpt is likely from the case Plessy v. Ferguson (1896). This was a landmark decision of the Supreme Court. It held that segregated facilities were constitutional as long as the facilities were equal in quality ("separate but equal"). The only dissent was written by Justice John Marshall Harlan. The decision is widely regarded as one of the worst in history, and it has been de facto overruled.