Does the punishment for slander (eighty lashes) apply to an Arab man who called another person "O Indian," considering this an accusation that the slandered person's mother committed adultery with Indians?

Qadhaf is accusing someone of zina (fornication or adultery), either explicitly or implicitly. So, if someone says to an Arab, "O Hindi (Indian)," he has indeed accused his mother of zina, and the Hadd (prescribed punishment) applies to him if he intended to deny his lineage. However, if he intended to liken him to Indians in character, then no Hadd applies to him.