I don't believe the "Helter Skelter" race war motive.
It's BS. Either the murders were a drug deal gone bad. One of the killers probably knew the victims likely Frykowski or Folger since both were heavily into drugs.
Or the other plausible motive is to do a copycat murder so the police wouldn't focus on Manson member, Robert Beausoleil , who was arrested for the prior murder of Gary Hinman just weeks prior. I believe Susan Atkins mentioned this in her book as to why the murders happened. Both the Tate/Labianca murders and Hinman murder had the victim's blood written on the walls.
Charles Manson already knew Terry Melcher didn't live there. He probably picked that house because Tex Watson already knew the layout. Plus, prominent people lived there and it was secluded. It was a symbol of Manson's rejection from Hollywood and to instill fear into Terry Melcher.