Final answer:
Justice Harlan believed that the true purpose of the Separate Car Act was to enforce racial segregation under the guise of 'separate but equal' accommodations. His dissent in Plessy v. Ferguson emphasized the Act's violation of the Equal Protection Clause of the Fourteenth Amendment, contrary to the majority opinion that upheld segregation laws.
Step-by-step explanation:
The true purpose of the Separate Car Act, according to Justice Harlan, was ostensibly to promote the comfort of passengers through segregation. However, the Act was effectively a tool for enforcing racial segregation and inequality. Justice Harlan, famously dissenting in Plessy v. Ferguson, recognized the law's true intent, despite its superficial claim of ensuring 'separate but equal' accommodations.
In his dissent, Justice Harlan argued that the Louisiana law and similar segregation laws were an affront to the Equal Protection Clause of the Fourteenth Amendment. His perspective, however, was not held by the majority, who upheld the constitutionality of segregation under the Separate Car Act. It wasn't until cases such as Brown v. Board of Education that the notion of 'separate but equal' was overturned and the path towards ending de jure segregation was laid.