Play video content EXCLUSIVE TMZ.com

John Mayer wants to can the idea that men must be alpha males and take what they want -- including women -- and replace it with a new doctrine focused on respect and sensitivity.

The guitar-slinging crooner was doing a cancer benefit show Sunday night at the Modell Performing Arts Center in Baltimore when he went off on a tangent about toxic masculinity, which he called a "bulls**t" alpha male contract that's nailed into boys' heads from a young age.

He says the sentiment that a man should get an erection at the sight of every woman he wants is crap. John added the so-called "trauma" men might feel when a woman turns them down ... is something men just have to get over.

His new idea on how to raise boys ... teach 'em that the world isn't theirs, and they're not definitely not entitled to every woman. It's worth noting this rant came right after John performed "Daughters."

He never calls him by name, but it's pretty clear John's referring to newly sworn-in Supreme Court Justice Brett Kavanaugh.