Don’t mess with Snoopy!

A mass of angry anarchists marched on the Macy’s Thanksgiving Day Parade in Midtown Thursday, pushing back at police and barricades as they made their way toward the procession.

Emboldened days after cops left them free to clog major Manhattan roadways, the throng pushed against police keeping them from the parade route a half-block away along Sixth Avenue.

Seven were arrested as they knocked down metal barricades.

Glass rained on the ruckus as a window was smashed on the 10th floor of a West 37th Street office building. Police were not sure how the window was broken.

“My kids were scared because the glass was coming down. The kids were crying. It’s horrible. We just came to see the parade. I drove three hours,” said bystander Elizabeth Matos, 33, of Boston.

“You have the fight, people being arrested, and the glass coming down. It spoils it for my kids.”

The hashtag “#StopTheParade” was burning up Twitter a day earlier as agitators planned a wave of fresh chaos after two nights of running wild to protest the Ferguson, Mo., grand-jury decision.

“The police aren’t going to arrest us, and they are not going to shoot us,” an organizer who called himself “Magiq” boasted Wednesday night to two dozen rabble-rousers at a protest-planning session in Union Square.

Sources told The Post that Mayor de Blasio had ordered the NYPD to back off the mobs that blocked the Lincoln Tunnel, Brooklyn Bridge and other major thoroughfares Tuesday night.

But early Thursday morning, Police Commissioner Bill Bratton vowed the NYPD would stop any attempt to crash the parade.

“We will not tolerate, under any circumstances, any effort to disrupt this parade,” he said at a breakfast for the families of emergency workers, cops and firefighters before the parade. “This is a national event, a historic event. Anybody who would seek to interrupt it would be callous, indeed, on this very special day.”

The protesters — whom cops stopped from reaching Snoopy, Thomas the Tank Engine and other balloons — massed at the New York Public Library at West 42nd Street. They marched down Fifth Avenue and turned right on West 37th Street, then tried to U-turn back to the parade route.

Told by cops that they couldn’t turn around, the crowd grew angry at about 9:20 a.m., with some knocking down metal police barricades as paradegoers fled.

Six protesters were given desk-appearance tickets for disorderly conduct, cops said. Another was issued a violation.

Some protesters claimed they were peacefully marching when cops started pushing them.

“The goal of today was to stop the parade and send a message. The Ferguson verdict shows a compete lack of respect for black youths,” said Khaleed Alston, 25, a teacher at Grace Church School who was arrested.

“Four officers picked up the metal barrier and started pushing us back, and that’s when the chaos started.”

“My girlfriend was getting bulldozed over by the barrier, so I reached out to grab her hand. As I try to grab her hand, an officer pulls me back into the street and shoved my face to the ground.”

Despite the ruckus and a bit of rain and snow, the nationally televised parade went off smoothly.

The event, which counted Thomas, Paddington bear and the Red Mighty Morphin Power Ranger among its six new balloons, began under a drizzle that was replaced by snow flurries by the time Santa Claus made his appearance at the end of the parade.

“To see this in person is really quite an experience,” said Dan Dashiell, 43, who brought his daughter Annie, 8, from San Francisco. “I had to wake her up early, because this is a once-in-a-lifetime experience.”

Additional reporting by Larry Celona, Dana Sauchelli, Natasha Velez, Ben Feuerherd and Post Wires