YOU don’t often see handwritten political posters in Edinburgh’s New Town, so I was struck by one I saw in a window on Tuesday. Referring to #BlackLivesMatter, it simply said “Scotland is not innocent”.

Too right we aren’t. There was much coverage last week about Scotland’s involvement in slavery and it is to our shame that there are still stone images throughout the country celebrating individuals with very dirty hands which no amount of philanthropy can clean.

There should not even be a debate about owning up to the injuries done by colonialism and racism. Scotland has been involved in, and profited from, both.

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Like the Mayor of Bristol, I cannot regret the actions of those demonstrators in her city who tore down the statue of a man responsible for the suffering and death of thousands, indeed tens of thousands, of human beings and who then threw it ignominiously into the harbour.

But the results of anger are unpredictable and indiscriminate. It can be cleansing but it can also be disfiguring. How can we build as well as destroy?

It goes without saying that not only do black lives matter but we must also make sure that we never again allow that fact to be decried or denied. Actions, as Anas Sarwar said so well in the Scottish Parliament last week, are what we need, not tweets or even columns. We must, without doubt, create a more just economy and a fairer society. We must also spread knowledge.

For example, the massive pillar topped by Henry Dundas in Edinburgh’s St Andrew Square must have some prominent new interpretation close to it that explains his equivocation on slavery, and his corruption as well. It is ludicrous that there has been any delay about this.

We must tell the truth in schools about individuals and society, and of course we should be prepared to re-describe our streets and to expunge other bizarre normalisations of racism such Dunoon’s Jim Crow rock in my own constituency, which needs to be repainted and renamed so that it can become an exemplar of how wrong it has been to tolerate such things and how determined we are to change them for ever.

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There are, alas, many other memorialised instances of racism and prejudice in our country yet, offensive as they are, changing them would mean little – as Humza Yousaf has pointed out – if we did not change the nature of society, too, so that not all our judges, our police chiefs, our council CEOs, our politicians or our chairs of major public bodies (to name just a few examples) are white.

But there is more. Slavery was often accompanied by conquest and it is simply obscene to pretend that the sum of human knowledge would be imperilled by acknowledging, and reversing, theft and desecration by returning stolen property to its historic owners.

If there is to be a museum devoted to Empire and slavery it must be one in which empty shelves testify to the fact that we have no right to the Benin Bronzes or Ethiopian tabots, or any other disgraceful loot.

Righting wrongs may go wider as well. My former colleague Rob Gibson has argued for a long time that the overweening edifice of the Duke of Sutherland on Beinn a’ Bhragaigh should be toppled because of his role in the brutal, dehumanising Highland Clearances.

Some argue that such iconoclasm rewrites history and that leaving the offending item in situ or counterpointing it with another nearby teaches people more about the uncomfortable issues it raises, a position that a real Highland philanthropist, my friend the late Dennis MacLeod, used to argue.

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I agree with him that it is usually better to get even than to get mad.

Yet occasionally one image suddenly stands for the whole.

Edward Colston in Bristol last weekend assumed a significance much bigger than himself – he became a totem of greed, inhumanity, cruelty and hypocrisy.

Years of injustice and years of trying to set the record straight came together in a single action that matched symbol for symbol. That which had stood insolently and permanently in reproach not just to decency but to an entire race was suddenly cast down and contemptuously thrown out of sight.

Metaphorically that is the job we must all do – cleanse our societies and communities of the crime which regards another man or woman as being of less worth than ourselves.

Only then can we free ourselves to create a better future for a better country.