Nothing like a piece of paper to scare a bureaucrat.

That the lesson a Massachusetts man learned last week when he flashed his gun license during an argument with his son’s principal — and ended up losing his license and his gun to police because the principal claimed he thought he’d been threatened.

According to the Boston Herald, the dispute began over a drawing by Roger Goodwin’s son depicting Gru, the character from the movie, “Despicable Me 2,” shooting ping pong balls at his “minions.”

The school’s principal Michael Hanna apparently considered the image sexual because the “minions” have a phallic shape.

During the argument, Goodwin pulled out his gun license to compare the gun depicted on it with the image his son had drawn to show his son had drawn a gun.

He then admitted he had access to firearms at home, which Hanna took as a threat, according to CBS.

Hanna summoned police and had Goodwin removed from the campus. The police chief in Arlington, Mass., about six miles north of Boston, revoked his license and police confiscated his hunting rifle.

“I did not threaten [Hanna’s] life in any way,” Goodwin told the Heraldt.

He has not been charged with any crime.

The school district, meanwhile claims the nature of the dispute and Goodwin’s flashing the gun license justified its actions of going to the police to have Goodwin banned from the school’s campus, have his gun license revoked and have his weapon seized from his home by police.

“This argument certainly went above and beyond the scope of a normal disagreement, and therefore the policies and procedures that Arlington Public Schools have in place were immediately activated to make sure that students, faculty, and staff remained safe,” the district said in a statement.

“Safe” is what bureaucrats always say when they’re the ones who are scared but want everyone else to be too. “Policies and procedures” is what they say when they want to sound tough. Instead they sound pathetic.

And this occurs on the outskirts of Boston, cradle of the American Revolution, where the first battle of the war was fought between British redcoats and colonials protecting a cache of weapons.

It just proves, guns don’t kill people, but gun licenses scare liberals.