About Johnson, Boswell writes:
The truth, however, is, that he loved to display his ingenuity in argument; and therefore would sometimes in conversation maintain opinions which he was sensible were wrong, but in supporting which, his reasoning and wit would be most conspicuous. He would begin thus: "Why, Sir, as to the good or evil of card-playing—"; "Now, (said Garrick,) he is thinking which side he shall take." He appeared to have a pleasure in contradiction, especially when any opinion whatever was delivered with an air of confidence; so that there was hardly any topick, if not one of the great truths of Religion and Morality, that he might not have been incited to argue, either for or against.
I must admit to being in sympathy with Johnson’s view. There is nothing that makes me feel more contrary than an opinion “delivered with an air of confidence”.