Today, movies like Finding Dory and Frozen are rated PG—Parental Guidance suggested. Parents can assure impressionable young children that, yes, they will eventually find Dory, and yes, it is okay to let it go.
But in the '60s, PG had a different meaning. The same rating applied to The Secret Life of Pets is applied to the secret life of British spies, a life that includes investigating the bloody murder of a man gunned down on screen by three assassins who then carry his bloodstained body into their hearse. These same men break into an office and murder his secretary in cold blood, leaving bloodstains on the carpet. Even James Bond shoots a man, then shoots him in the back multiple times.
On top of this, a man is roasted to death by a fire breathing dragon tank (don't ask) and another man falls into boiling water. To sex things up, Bond seduces three women and takes a naked shower with one. Yes, they're washing off irradiated water from a swamp, which is pretty un-sexy, but that doesn't stop the camera from lingering on both their bare soapy bodies.
Long story short: parental guidance suggested.