[A]ny broad unlimited power to hold laws unconstitutional because they offend what this Court conceives to be the ‘conscience of our people’ ... was … - Hugo Black

President Roosevelt [...] told me there was no reason for my worrying about my having been a member of the Ku Klux Klan. He said some of his best friends and supporters he had in the state of Georgia were among members of the organization. He never in any way, by word or attitude, indicated any doubt about my having been in the Klan nor did he indicate any criticism of me for having been a member of that organization.

History indicates that individual liberty is intermittently subjected to extraordinary perils. Even countries dedicated to government by the people are not free from such cyclical dangers. ... Test oaths are notorious tools of tyranny. When used to shackle the mind they are, or at least they should be, unspeakably odious to a free people. Test oaths are made still more dangerous when combined with bills of attainder which like this Oklahoma statute impose pains and penalties for past lawful associations and utterances.... Governments need and have ample power to punish treasonable acts. But it does not follow that they must have a further power to punish thought and speech as distinguished from acts. Our own free society should never forget that laws which stigmatize and penalize thought and speech of the unorthodox have a way of reaching, ensnaring and silencing many more people than at first intended. We must have freedom of speech for all or we will in the long run have it for none but the cringing and the craven. And I cannot too often repeat my belief that the right to speak on matters of public concern must be wholly free or eventually be wholly lost.

That Amendment requires the state to be a neutral in its relations with groups of religious believers and nonbelievers; it does not require the state to be their adversary. State power is no more to be used so as to handicap religions than it is to favor them.