The Prophet (pbuh) said, “he/she who defends the honour of his/her (Muslim) brother/sister, Allah swt will secure his/her face against the Fire on the Day of Resurrection.” [Tirmidhi].
The Messenger of Allah (pbuh) said, “Do not abuse the dead, because they have attained that which they had forwarded (i.e., their deeds, good or bad).” [Bukhari].