PUP councillor John Kyle has been kicked off his bicycle after he tried to stop four men in their late teens from defacing a memorial to David Ervine in east Belfast.
The men were by the mural to the late PUP leader when Dr Kyle spotted them at around 8.20am on Sunday.
He said one of the men was defecating on a memorial seat while another man was filming him.
The mural is on Montrose Street, close to Albertbridge Road.
Police said they are investigating the report of an assault on a man in the Albertbridge Road at around 8.40am on Sunday.
They are also investigating a report of attempted criminal damage.
Dr Kyle said he chased the four teenagers but they later spotted him and kicked him off his bike.
"I was able to go on, but that's not the important thing," he said.
"I think defacing a memorial on Remembrance Sunday is what people have found most offensive.
"People have been very angry and upset at this mindless vandalism."
Dr Kyle said the chair forms part of a sculpture to commemorate Mr Ervine's life.
"The empty chair represents that David is no longer with us," he said.
"The one positive thing to come out of this is that there has been widespread condemnation of this from across the community.
"David Ervine was a man who was very committed to bringing peace to inner east Belfast.
"He was very highly respected by his contemporaries in both sides of the community.
"That's why this is doubly offensive, because of the type of man David was."
Sinn Féin senator Niall Ó Donnghaile, from the Short Strand area of east Belfast tweeted: "I've spoken with my colleague John Kyle a number of times today. He has mine and Sinn Féin's full solidarity and support."
Alliance leader Naomi Long, who represents East Belfast, urged anyone with information to contact police.
"This kind of disrespect is shameful. Thoughts with Jeanette and family and John Kyle," she tweeted.
North Belfast MLA Nichola Mallon tweeted: “Hope you are ok John Kyle. Shocked to hear about this despicable attack but not shocked to hear it was you who stood up to these thugs.
Deputy First Minister Martin McGuinness said the attack was “unacceptable”.
“Disgusted at the attack on PUP’s John Kyle confronted those responsible for violating an east Belfast memorial.”
Alliance East Belfast MLA Chris Lyttle also condemned the incident.
"There can be absolutely no excuse for the attack on Councillor Kyle or the disgusting behaviour at the memorial to Mr Ervine," he said.
"I would urge anyone with information to pass it to the police or the Crimestoppers charity.”
Mr Ervine, a former member of the UVF, died in 2007 at the age of 53.
He was jailed in the mid-1970s after being found with explosives.
Several years after his release in 1980, he became a politician and helped bring about the 1994 loyalist ceasefire.
