死し者しゃに鞭むち打うつ

expression, godan verb (-tsu)

speak ill of the dead; criticize the dead

Idiomatic expression meaning to criticize or badmouth someone who is already dead and cannot defend themselves. Often carries a nuance of pointlessness or cruelty.

• もう亡なくなった人ひとのことを悪わるく言いうのは、死し者しゃに鞭むち打うつようなものだ。

  Speaking ill of someone who has already passed away is like flogging a dead horse.