Nicked from Aquinas via Shrine of the Holy Whapping, who need to get their permalinks together.

It is against reason to be burdensome to others, showing no amusement and acting as a wet blanket. Those others without a sense of fun, who never say anything ridiculous, and are cantankerous with those who do, these are vicious, and called grumpy and rude.
Aquinas, Thomas. Summa Theologica. Trans. GilbyII-II.cxlviii.4.