Floyd went after Oscar earlier Thursday -- posting an old photo of De La Hoya wearing fishnet stockings and heels -- and saying, "I fought her and her name is Oscar 'Golden Girl' Dela Hoya."

Floyd then implored his fans on social media to "leave the most disrespectful caption you can think of" about Oscar.

Now, Oscar is firing back ... saying, "Hey, [Canelo Alvarez] someone is salty about your record breaking contract with @dazn_usa. Good thing we will never resort to hitting women."

He added some hashtags -- "#DomesticAbuser #DomesticViolence #Salty #antidomesticviolence #FloydMayweather #SaltyFloyd #FloydSaltyMayweather #whyyoumad."

Of course, Floyd was convicted of domestic violence in 2011 stemming from an incident where he attacked the mother of his children. He cut a plea deal and served jail time.

Unclear what Floyd's endgame is in regards to the feud with Oscar and Canelo -- since it seems he's already 86'd the idea of a rematch with Canelo.

Maybe these guys just don't like each other.