NBC hung Brian Williams out to dry, and guaranteed he will never return to its "Nightly News" desk ... according to veteran news guy Geraldo Rivera.

The "Celebrity Apprentice" runner-up told us Williams got a raw deal when NBC suspended him for 6 months, because it prolonged the inevitable -- what he calls a "death penalty" to BW's career.

Geraldo added ... the Peacock should've just ripped off the band-aid and canned Williams now. Not that he thinks that would've been fair.

Watch the video ... it's the staunchest defense we've seen yet -- blasting network execs and everyone who's judging Brian from "the safety of their parents' basement with their hands on their computer saying tsk tsk."

We smell a budding bromance.