The Big Issue in the North magazine has dropped an advert for a drugs company after one of its vendors was attacked by an animal rights campaigner.
The Big Issue in the North is sold in 120 UK towns and cities
The homeless man was selling the magazine in Liverpool when he was assaulted by a woman over its adverts for Covance, which tests on animals.
Big Issue Managing Director Richard Brown called it a "horrific incident".
A Merseyside Police spokeswoman said police patrols had been stepped up in the area.
She said the force could not take the incident further as the vendor did not want to press charges.
The incident happened on 8 July in the Concert Square area, Mr Brown said. "We will not put the safety of our vendors at risk and feel we have no option other than to stop running the Covance adverts in the magazine," he said.
"Picking on vulnerable people to get what you want is a despicable way to act.
"The Big Issue in the North works with people who are victimised.
"Our vendors are 13 times more likely to be attacked in the street than any other member of the public.
"People should be supporting vendors and organisations like The Big Issue in the North to tackle inequalities and not reinforcing them."
The Manchester-based magazine will lose £2,500 per year by dropping the Covance adverts.
A Covance spokesman said: "It is a great shame that the Big Issue in the North, which does a great deal to help disadvantaged people to help themselves, has been forced into this position.
"They have done what they had to do because their vendors were vulnerable and their safety has to be the primary concern.
"Our anger is directed only towards those people who would attack a magazine vendor simply because the magazine doesn't agree with their views."