Dave Bautista is really, really, REALLY mad at whoever spray painted the n-word at LeBron James' L.A. home ... blasting the racist perpetrator as the "scum of the Earth."

In fact, the "Guardians of the Galaxy Vol. 2" star was getting angry even talking about it with TMZ Sports -- and took a breath to calm down.

TMZ Sports broke the story, LAPD units responded to Bron's home around 7 AM on Wednesday. No arrests have been made so far.

Bautista HATES racism. Hates bigotry. Hates intolerance ... and says he truly feels for LeBron.