An 1860 guide for a gentleman’s conduct in conversations.

One of the first rules for a guide in polite conversation, is to avoid political or religious discussions in general society. Such discussions lead almost invariably to irritating differences of opinion, often to open quarrels, and a coolness of feeling which might have been avoided by dropping the distasteful subject as soon as marked differences of opinion arose. It is but one out of many that can discuss either political or religious differences, with candor and judgment, and yet so far control his language and temper as to avoid either giving or taking offence.

The Gentlemen’s Book of Etiquette and Manual of Politeness, by Cecil B. Hartley