Adel Defilaux, a French-born Muslim, was terrified when a man stormed into The Antishop in Brick Lane, East London, at 9.30am yesterday.
The intruder demanded that Mr Defilaux take down the sandwich board featuring the slogan that has become a rallying cry in support of the 12 victims of Charlie Hebdo massacre in Paris.
But when Mr Defilaux, 32, calmly protested the man became aggressive and warned that anyone who supported the French satirical magazine should die.
He said: “He came in very aggressively and he told me to remove the sign. I asked him why and he said his community was offended by it and said if I didn’t remove it something bad was going to happen.
“I told him I was Muslim myself and I wanted to talk gently with him and I said people can’t kill journalists for expressing themselves.
“I calmly explained to him that what he was saying was not the reality of Islam. I thought I could calm him down, but it had the opposite effect. He went crazy.
“He said ‘I believe these people deserve to be killed and anyone supporting them deserves also to be killed’.
“I was all alone and started getting scared. He was a dangerous person. He said if I didn’t take down the sign he would smash up the shop, and then he just left.”
Mr Defilaux, who is originally from Marseille but has lived in London for five years, said he had put up the sign to support everyone in France and had received no complaints from anyone else.
“I get on with all the community here. We are opposite a mosque and all my neighbours are Muslim and no one else has had a problem with the sign. These fanatics believe in the wrong stories and have no shame in attacking people,” he said.