All it does is....

[Mike Hussey]

Dave Moss frustrated about his real estate sales business:

Dave Moss: They don't give you the leads, they don't give you the support, they don't give you d*ck. Then they're yanking us in on a sales conference. When did anyone make a dime or learn a goddamn thing? All it does is some jerk shoots his mouth off.

What does "it" in "All it does is" refer to?

Source: Glengarry Glen Ross (a 1992 American drama film adapted by David Mamet from his 1984 Pulitzer Prize–winning play of the same name, and directed by James Foley)

 

[GoesStation]

Nothing in particular. The screenwriter has reproduced conversational English more accurately than most dialog does. The speaker has forgotten exactly what he said in the previous sentences.

Do you understand the sense of the statement?

 

[Mike Hussey]

Nothing in particular. The screenwriter has reproduced conversational English more accurately than most dialog does. The speaker has forgotten exactly what he said in the previous sentences.

Do you understand the sense of the statement?

Dave refer with the word "they" this "it" should refer to their boss/supervisor?

 

[GoesStation]

He means Only one thing happens at a sales conference: some unpleasant person says a lot of nonsense.