Hilchos Lashon Hara chapter 8, section 1

This chapter will go into more details concerning the prohibition of speaking and listening to lashon hara.
1. The prohibition applies to man, woman, relative or non-relative. Even though a person is generally does not mind when a relative speaks lashon hara about him, and even though a person generally does not intend to disparage his relative but rather, is upset at a perceived wrong-doing of the relative, nonetheless, if he hurriedly judged the relative harshly and he actually did not do a wrongdoing, this is absolute lashon hara.