Police in Glasgow are continuing to guard a statue of William of Orange amid fears it may be targeted by activists aligned with the Black Lives Matter movement.
The statue, which has already been daubed with an anti-police slogan and the letters IRA in the last week, is deemed at risk because of claimed links between King William and the slave trade.
While it is claimed that the monarch took over the Royal African Company, which was centrally involved in the trade in the 17th century, historians say that it is not entirely true.
Following lobbying by Bristol merchants and others, in 1698 William allowed other traders to compete with the Royal African Company, which until then had a monopoly on the business of shipping slaves, mostly from Africa to the Americas.
The Crown took a portion of the profits of slave trading throughout its history until it was abolished in 1833.
Jim McHarg, grand master of the Grand Orange Lodge of Scotland, described the vandalism of the statue, first erected in 1735, as upsetting.
"King William brought liberty and took away the divine right of kings and the tyranny associated with that. It is very strange to hear he is connected with slavery. He is part of the history of Great Britain," Mr McHarg told the Glasgow Times.
"This has come from republican and socialist people who hate everything that is unionist."
It is a sign of the growing tension around statues and monuments, which has spread to Northern Ireland.
In a separate move, Amnesty International has called on the people of Larne to consider renaming the McGarel Town Hall because of its links to a plantation owner and slave dealer. It is named after Charles McGarel.
Patrick Corrigan from Amnesty International told Sunday Life: "He would have been one of the biggest recipients of compensation and I'm not sure there are many locally who would have been as involved in the slave trade.
"There's an opportunity here, to think is that the message they want to send out today, are those the values we share and celebrate?"
McGarel - who lobbied strongly against the abolition of slavery in the West Indies - and his companies were paid £81,280, close to £10m in today's money, in compensation following its ending.
Activists have also called for the replacement of a statue of Co Down-born physician Sir Hans Sloane, because he was married into a family that owned a sugar plantation in Jamaica.
The statue of Sloane stands in Knightsbridge, west London, while a copy of it was erected in his home town of Killyleagh.
A campaign is now under way to replace Sloane's statue with a tribute to former Chelsea footballers.
DUP councillor Billy Walker described the campaign as "ridiculous".
He said: "This man did so much for the world - he gave us the concept of free museums; he found a cure for smallpox; he pioneered science and medicine to do away with magic for treating illness; he promoted the use of quinine against malaria; he discovered milk chocolate; he was the first man to lead both Royal Colleges; he treated the poor for free.
"The list is endless. He was no slave trader."
Online petitions have also been started calling for the removal of Irish pro-slavery advocate John Mitchel's statue in Newry.