"When you omit courtesy you're throwing sand in the gears of a machine that doesn't work too well in the first place."

~Heinlein (I'm paraphrasing.)

There's no glory in being a boor, and no shame in being courteous.

None of this is news: https://en.wikipedia.org/wiki/Etiquette#History

    A fool never learns,
    A man learns from his mistakes,
    A wise man learns from the mistakes of others.