He spoke to his father Yaakov about some things that he felt his brothers were doing wrong. He loved them and had only had their best interests in mind. The Chofetz Chaim explains that one must tell the person directly about his fault. Every word that he said was measured, weighed, and then sent back to him. That is what I mean by the measure of a word.
Good words are stronger that the latest wonder drugs.
They can make a person feel great, build up his confidence, even develop his talents. Bad words, G-d forbid, on the other hand can be more powerful than bombs and bullets. They can embarrass, depress, or even break a person. Yosef's words caused him to be sold as a slave, a pretty miserable fate. That's what I'm getting at Chaim.