Clean Language

The Gemara in Pesahim (3a) asks why the Torah, in describing the animals Noah was to bring onto the ark, refers to non-kosher animals as "einenah tehorah" (that are not pure) rather than the more simple "temei'ah" (impure). The Gemara answers that it was in order not to record a negative term. Better to add extra words than to include a negative term.

However, this is difficult because there are many clearly negative terms in the Torah. The word "temei'ah" is, in fact, used in the Torah! The Ba'al Ha-Ma'or explains that when the Torah is teaching a specific point then it is appropriate to use the negative term. However, in other contexts -- such as telling Noah what animals to bring onto the ark -- there is no specific need for a negative term and therefore it is inappropriate.

The book Ha-Ga'on by R. Dov Eliach (vol. 3, pp. 922-923) records a story in which one of the Gra's students was talking to the Gra and used a derogatory term for Hassidim. The Gra reacted negatively and the student pointed out that the Gra himself had used much harsher terms. The Gra answered that when explaining his opposition to Hassidim, the context called for using strong and negative terms. But in other contexts, it is inappropriate to use negative terms.