Serial transit thief Darius McCollum — whose criminal career is the inspiration for an upcoming Hollywood movie — is a “guardian angel” who should be played by Denzel Washington, his lawyer said outside Brooklyn court on Monday.

Sally Butler, who will be played by Julia Roberts in the movie “Train Man,” rejected a deal for his client to serve five to 10 years on a plea to grand larceny for stealing a Greyhound bus from the Port Authority Bus Terminal last November.

Outside of Brooklyn Supreme Court, she painted McCollum, 51, as a victim who has made the city safer.

Butler, who suggested that Washington might play her client, said: “This is a good guy. We need to ask him to help us. He can keep us safe. He made our subways safe; he can make our streets safe. He is our guardian angel.”

She said her client worked for the MTA after 9/11 by flagging security problems, but an MTA source denied the claim.

Butler said that murderers get more lenient deals from the Brooklyn district attorney than her client.

“This is not justice. You can kill someone here and get less time than 10 years,” she insisted.

MTA spokesman Kevin Ortiz vowed the agency would “pursue recovery under the New York state Son of Sam law against Mr. McCollum for any ill-gotten gains he receives from participation in this purported film project.”

McCollum, whose obsession with the transit system stems from his Asperger’s syndrome, was first arrested in 1980 at age 15 when he took an E train for a joy ride.