EXCLUSIVE

NBC sent a "goon squad" to manhandle a "Today" show audience member because he's a known Trump supporter and they hated his t-shirt ... according to the guy's new lawsuit.

Mark Gallagher claims NBC security descended on him and roughed him up last month because he was pro-Trump ... according to the docs. He says he was doing nothing wrong at the time -- just chatting 2 ladies and wearing an anti-Clinton shirt.

Gallagher admits he had a motive for being in the "Today" audience ... he believes Bill Clinton is a rapist, and wanted to get some TV time for a shirt with Bill's face and the word "RAPE" on it. He says he was successful doing this the day before on "Good Morning America."

According to the suit ... Gallagher was assaulted by the goons before he even had a chance to take off his sweater and reveal his shirt. He claims he was struck in the back of the head with a security radio and sustained injuries to his neck, lower back, ribs, arms and ankle while being removed ... and has bruises to show for it.