How sound is the Hadith, "Peace be upon you and upon your mother," and does it indicate the permissibility of belittling the transgressor and his parents?

This hadith (definition) is weak due to discontinuity in its chain of transmission, discrepancies in its narrations, and the anonymity of some of its narrators. The phrase "upon you and upon your mother" does not imply disrespect; rather, it indicates that the salutation was given in an inappropriate context. The correct teaching in this regard is the hadith of Abu Hurayrah, which specifies what should be said when one sneezes and what should be said in response to one who sneezes.