Former Royal Engineer's Lance Corporal Derek Hardman told staff they were responsible for any "bad blood" after banning him from a veteran's event.
Police visited the gun-toting ex-soldier after the intimidating picture was sent and told him that a female council employee felt threatened by the photo.
Hardman has been at war with Hull City Council over their decision to ban his group of veterans from the city's Veteran's Weekend event.
The local authority wasn't happy with the veteran group, called Barker's Breakfast Club, after its behaviour at last year's Veterans Weekend held at Hull, East Yorks.
It accused the ex-soldiers, who meet every Saturday, of aggressive behaviour, of drinking alcohol and undertaking unsafe practices at the family event.
Mr Hardman said: "I did not send the photo to threaten. I was accused of being threatening towards that person at last year's event, so I sent her a clear facial shot, taken on that day, to prove it wasn't me.
"The photograph was clearly marked , 'This is a photograph of me last year at Veterans Weekend.'"
He says his assertion that veterans would not "walk quietly away" should not have been seen as a veiled threat, and insists it was not even sent to the female council worker who complained.
"She has seen the photo and read the closing lines of my previous email to another council officer, which states, 'This is unfair and it is wrong!'
"This is the very last thing I wanted - any sort of bad blood or conflict with Hull City Council, but you are giving us no choice.We simply cannot allow this to continue.
"Do you assume that we, as veterans, will shrug our shoulders and walk quietly away?
"Last year the first time we had exhibited. I made a few small errors, but nothing that should have excluded us this year."
Responding to the claim that they had drunk too much alcohol, Mr Hardman said: "A couple of veterans who'd been on their feet all day flopped into a couple of chairs and opened a bottle."
The council was also peeved that a banned generator had been used hidden in bushes.
"It was a clearing in the bushes to prevent any person going near," said Mr Hardman.
Mr Hardman also denies the council's claim the group was responsible for "unauthorised vehicle moves".
He says an event organiser gave the group permission to collect a wounded veteran.
In a statement, Hull City Council said: "The safety of visitors and those taking part in the Veterans Weekend event in East Park is of paramount importance.
"If organisations contravene the clear guidelines and rules needed to ensure the event can be safely enjoyed by our many visitors, we cannot allow them to be part of this hugely successful weekend.
"There were a number of issues with this organisation at last year's event, including consuming alcohol, aggressive behaviour towards council staff and use of unauthorised equipment."
Humberside Police said: "We wouldn't confirm details relating to a named individual."
Reporting by SWNS/Ross Parry