The Labour peer and former Defence Secretary insisted he would not be shouted down by those who, he says, have branded him scum, vermin and a "pestilential parasite".
He said he had taken heart from friendly voices across Scotland who "support what I say but dare not say it themselves for fear of being thrown to the wolves".
Last week, Lord Robertson sparked controversy when he warned a Yes vote in September would be "cataclysmic" for the West and that if independence ever came to pass "the forces of darkness would simply love it".
The Yes camp publicly denounced his "apocalyptic" remarks; First Minister Alex Salmond mocked them during his speech at the SNP conference, claiming the No campaign had become "totally laughable and completely ludicrous".
The No camp privately denounced his words too, saying they were "over the top" and unhelpful in the Whitehall bid to project a more positive message for the Union.
However, in an article for the Scottish Review, Lord Robertson underscores the high stakes, describing the referendum as the single most divisive political debate ever undertaken in Scotland, which has "split it right down the middle".
He explains: "In my political career, I grew a thick skin. I used to remark that when I became Secretary General of Nato, dealing with global terrorism, tension between states, organised crime and piracy was a walk in the park compared to Scottish politics. And so last week proved my point.
"Many people have taken me to task. I was called scum and vermin and a pestilential parasite, among other things. But I won't be shouted down by these people.
"Nor will I be shouted down by my political opponents who throw insults but who will not engage on the substantive issue, which is the world outside Scotland cares about the decision we are about to take, and, like it, I passionately believe it will diminish the UK's position in the world."
He takes Deputy First Minister Nicola Sturgeon to task, saying she went on the radio to say that on the one hand she was not surprised by his views but on the other was shocked by them.
"Not once did I hear her engage on the material point I made. Instead, the well-worn Scottish National Party tactic of distraction was deployed and the response to my speech focused largely on one word and a handful of other sentences."
"It is a bit like telling the children to look up at the sky when the ice-cream van is passing. People are not fooled by it."
Lord Robertson stresses that whatever the result of the referendum, it is an indisputable fact it will not just affect the people of Scotland but those across the UK and beyond. "The whole foundation of the United Kingdom will be altered and its place in the world will be changed," he says.
Using conspicuously more moderate language, the Labour politician again warns of the dangers of independence, noting that wherever he goes, he is asked about the referendum.
Declaring his love for Scotland and Britain, he writes: "Universally and unanimously, people say they don't want Britain to break up. Some will of course say it because they don't want change and like the status quo. Others, the majority, see the break-up of Britain as being a profoundly destabilising move in a fragile and unstable world.
"None of those people is paranoid. None of them is anti-Scottish. They are not opposed to self-determination. They just see Britain as being a major power in the world and indeed a powerful force for good. They see its fragmentation as unhelpful and damaging to Western solidarity."
He adds that there were those who disagreed with his politics who regretted that the debate had descended to a personal level that "bears no reflection of the important question we Scots are being asked to answer on September 18".