subjunctives - "demands that he abandon" vs. "demands that he abandons"

On a site about movies, I read the following:

While Nader defaults to self-righteousness after his wife demands that he abandon his Alzheimer’s-ridden father, Maadi shades the character’s stubbornness with layers of pained love that he’s never been taught how to express.

My question is about the first part of the sentence. why does it read "... he abandon.." instead of "he abandons"?

And I'm not sure about the meaning of "defaults to self-righteousness".