A digger is believed to have been used to demolish a monument erected in memory of two IRA members killed by the SAS.
The stone memorial at Drumfurrer in Co Monaghan was destroyed in the attack earlier this week.
It was dedicated to Jim Lynagh and Padraig McKearney, who were killed in an SAS ambush in Loughgall in 1987.
A fundraising campaign has been launched on the website GoFundMe to restore the memorial, which was built in 2007.
Ex-Special Branch officer Dr William Matchett, now an author, said it is inevitable that people will be hurt by the campaign to rebuild the monument. But he said that vandalism of any memorial was wrong.
"The men are dead and they have their families and anybody who defaces any memorial, it's just wrong and I'm sure it's being treated like a crime," he said.
"It ties in with the issues of victims and their pensions and equivocation - you can see it becomes very polarised.
"One section of our society hails them as heroes. Another swathe of society will say that they were armed terrorists who were trying to murder police officers.
"This legacy regime hasn't really brought any reconciliation that I can see.
"You have these two controversial figures in Lynagh and McKearney and a monument and people will say it's great this was destroyed, whereas I would see (it) differently.
"Whatever way you disagree with them, whether you think as I do that they waged a war against society, people have the right to pay respect to their dead," he added.
In a joint statement Mairead Kelly and Roisin Ni Cheallaigh of the Loughgall Truth and Justice Campaign condemned the attack.
"To do this to any of the Loughgall families is to do it to us all," they said. "It is a very upsetting... but our memories and thoughts cannot be erased."
The fundraiser has raised almost €3,000 of a €10,000 target.
Organisers said the money will go towards rebuilding the monument, including installing a new headstone and surroundings, new fencing and towards the upkeep of the monument.
Six other IRA members and a civilian also died in the ambush, which was launched as republicans attacked the RUC station in the village.