He might then have managed to avoid the misery of witnessing first-hand the horrors the international arms trade has inflicted on some of the poorest people in the world.
He could have delegated the task of fretting over the horrific human toll it inflicts – a person dies every single minute as the result of a firearm incident – to someone less personally scarred by such a violent loss.
That split-second moment of someone else's madness, played out in the otherwise idyllic surroundings of a Turkish seaside town, left him feeling that he had no choice.
"I suppose I have got a bit of an obligation. I need to do it," he says softly, referring to an emotionally debilitating commitment to play his part in the campaign aimed at stamping down on the international arms trade.
"I need to see it through. To see an international arms treaty would at least bring some satisfaction from knowing that we've helped make sure others don't go through what we are still going through now."
Today David, 36, is slightly more upbeat than he might be otherwise. The international anti-gun campaign he has fiercely supported since that crazed man sprayed bullets around a cafe and fatally wounded toddler Alistair has just notched up a minor victory on the United Nations stage.
Last week's vote to move a stage further towards an international arms treaty received the support of 147 nations – only the US and Zimbabwe refused to back it.
It's not quite the end of the present unrestricted arms trade – which, campaigners argue, enables powerful countries to saturate trouble spots with weapons, fuelling aggression, poverty and suffering – but it does move in the direction of a legally binding contract, which David hopes will save lives.
"It's a big move forward," he nods, "but everything seems to take such a long time. I remember being so happy in December 2006 when they agreed to work on this. That seems a long time ago now."
What feels less dated, however, is the brutal act that claimed Alistair's young life. While David, a printer, has thrown his energy into supporting the multi-charity organisation Control Arms Campaign – even travelling to Kenya to witness first-hand the horrors there – he can't escape the events of July 2003, when his two-year-old son became the innocent victim of a squabble between two men, one of them armed.
David had just returned home to Scotland after a happy holiday at his Turkish-born wife Ozlem's family's property in Foca, leaving her behind to enjoy a few more days with their son and her family.
She was in a local caf with relatives, Alistair was peaceful in his buggy, when a dispute flared at the next table. Someone pulled out a gun and bullets were sprayed across the caf.
Terrified, Ozlem and her family, including her 82-year-old grandmother, fled, hauling Alistair's buggy towards the seafront. It was only there they noticed his clothing drenched in blood.
The couple were overwhelmed with grief, but they also had a burning desire to do something positive. With Ozlem's support, David put his energy into highlighting the devastation weapons can bring. They worked initially on their own campaign in Turkey, where guns are status symbols and there are eight million of them among 70 million people, before teaming up with Oxfam and the Control Arms Campaign.
It has propelled David into the role of figurehead and spokesman for the anti-gun message, even though it means having to tell of his son's death over and over.
"The hardest point is where I have to discuss what happened to Alistair," he says. "I try to see it as a few minutes I've got to get through."
He has told Alistair's story across the world, including in Turkey, where his campaign has helped tighten laws and bring harsher sentences, and in Africa where the impact of unrestricted arms dealing is most severely felt.
"We crazily started an anti-gun campaign in Turkey after it happened. We had to do something or we'd have gone crazy. We got 300,000 signatures of support. That gives you faith in people. It made us believe that people don't want to live with guns."
He soon realised the scale of the problems guns create around the world: "It has been difficult to keep on being involved," he admits. "There was a family in Turkey, their son was eight, they were at a wedding when the local councillor pulled out a gun and fired it in the air as a celebration. What goes up also comes down. The boy was killed – tragic."
Few experiences were more challenging than his trip to Kenya.
"It changed how I thought about Africa, about myself and the world. You see that poverty and realise a lot of it is caused by the way we live. There are arms going in there and they make people who don't have great lives anyway that much worse.
The personal stories we heard were heartbreaking."
It was as he stood before more than 100 gun-totting tribesmen telling Alistair's story, that he was struck by the massive challenge anti-gun campaigners face.
"I was talking about what happened and what we are hoping to achieve, then it struck me I was talking about losing a son to people who have lost whole families; that everyone in each of those families has a gun; and they are sitting alongside the people who have killed their families. It was bizarre, shocking.
"What's interesting is that the countries that most support an arms treaty are the ones most affected by what arms can do because they are suffering the most."
Yet it would be wrong, he warns, to regard the unrestricted arms trade as a problem confined to a handful of impoverished nations.
"A person every minute becomes a victim of arms. There are eight million firearms produced every day with no controls as to where they end up. Recently in Harlem a gun amnesty brought in 744 guns – AK47s, handguns – just from a few streets.
"Children are dying here too," he insists. "Andrew Morton in Glasgow, killed by an airgun. The horrible tragedy in Liverpool of little Rhys Jones. Dunblane . . . John Crozier, whose daughter Emma died at Dunblane, has been a huge support."
Driving home the anti-gun message has given him something other than grief to focus on. Having moved to Gorgie from East Kilbride, David says adjusting to a new life without Alistair has been hard.
"Does it become less difficult living without Alistair? No it doesn't," he says sadly. "I can never find the words to explain what it's like.
"We went to visit grandparents in an idyllic little seaside town that was so quiet and peaceful.
"It could happen to anyone . . ."
For further information go to www.controlarms.org.
TAKING CONTROL OF SMALL ARMS
THE Control Arms campaign was launched in October 2003, consisting of Oxfam, Amnesty International and International Action Network on Small Arms (IANSA).
In December 2006, the campaign won a major victory when UN member states voted for work to begin towards a global Arms Trade Treaty covering international transfers of conventional arms. Last week's vote took work towards a treaty a step further, giving the go-ahead for vital talks towards a legally-binding document.
The campaign estimates as many as half a million people are killed directly with conventional weapons every year. It puts the global arms export market at $21 billion per year and estimates there are 639 million small arms in the world – one for every ten people.
Eight million more small arms are produced every year, along with 16bn units of ammunition – more than two new bullets for every man, woman and child on the planet.
Nearly 60 per cent of small arms are in civilian hands, and up to 90 per cent of illegal small arms start in the state-sanctioned trade.
The five permanent members of the UN Security Council – France, Russia, China, the UK, and the US – together account for 88 per cent of the world's conventional arms exports. The US, UK and France regularly earn more income from arms exports to Africa, Asia, the Middle East and Latin America than they provide in aid.