Two police union honchos are so outraged the NFL threatened to sack a Titans linebacker for wearing a patriotic pair of cleats honoring those who died on 9/11, they promised to pay his fine if he wears them in Sunday’s game anyway, The Post has learned.

Avery Williamson, a starting linebacker for the Tennessee team, hoped to wear a pair of specially-designed cleats at his team’s home opener Sunday against the Minnesota Vikings on the 15th anniversary of the 9/11 attacks, but he backed off when a league rep vowed to fine him for violating the league’s uniform code.

The left cleat says 9-11-01, with the 11 in the outline of the Twin Towers, while the right one says Never Forget.

“I don’t want to draw negative attention, so I’m just going to focus on playing the game,” Williamson told the Tennessean newspaper, on Friday.

The news outraged Paul Nunziato, head of the Port Authority Police Benevolent Association.

“I’m making a goal line stand on this. Enough is enough! The NFL is out of bounds on this,” he insisted.

He said that NFL Commissioner Roger Goodell, by denying Williamson the right to wear the patriotic footwear, had “committed a personal foul against humanity.

“This guy [Williamson] was hoping to honor everyone who died on 9/11, no matter what their country or color.”

Nunziato has teamed up with Patrick Colligan, president of the 33,000 member New Jersey State Policemen’s Benevolent Association, who was equally flabbergasted about the threatened fine.

Both union leaders say they’re urging Williamson to reconsider and wear the cleats – and the two unions will pay his fine.

“Paul and I said, ‘Let’s split his fine.’ If he [Williamson] agrees to wear these cleats, we’ll pay whatever fine he gets,” Colligan said.

“We want him to wear the cleats and we’ll pay the fine. He [Williamson] was absolutely doing a great thing and the NFL is threatening with a fine? When is Godell going to recognize what his fan base is?

“Here’s a player honoring those who died on 9/11 with a pair of cleats that he had made up himself — it’s not like he’s kneeling during the national anthem or anything,” Colligan said, a reference to the controversial decision by San Francisco 49er quarterback Colin Kaepernick not to stand during the national anthem.

Colligan said when he first came across the news about the NFL’s plan to fine Williamson for his plan to wear the cleats he “had to read the story twice.”

Even more galling, he added, is the realization that Kaepernick was not disciplined when he was spotted recently wearing a pair of socks during a team practice that depicted cops as pigs.

“Kapernick can wear ‘pig socks’ and not even garner a response from the NFL, but this guy wants to honor those who tragically died on 9-11 and he’s threatened,” he noted.

Williamson plans to auction the cleats for charity.