An important lesson learned from פרשת נח is the importance of using clean speech. We are to be careful about what comes out of our mouths just as we are to be careful about what goes in our mouths.
This idea is learned from the description of the animals that went into the ark. The animals that were fit for sacrifices were called בהמה טהורה, pure animals of which seven were taken. Those not fit for sacrifices were called בהמה אשר איננה טהורה, the animals that were not pure. Because the Torah did not use the word טמא, unclean, that has a derogatory connotation, we learn that we should always use clean language.
The Rabbis further say, לעולם אל יוציא דבר מגונה מפיו, that one should never let something inappropriate come out of his mouth. In short, watch your mouth!