The Boomtown Rats frontman said England and Scotland had together "invented the modern world" and argued the 21st century should be about interdependence, not independence.
Sir Bob is due to return with the band for a gig in Glasgow in October and hopes Scotland will still be part of the Union.
He said: "Nationalism is a very dangerous political animal. I know this - I'm Irish. It's a cheap political trick which twists the understanding of who we are.
"I completely understand the emotional impulse towards independence. But always consider independence in inverted commas because what the f*** does it mean?
"We are entirely dependent on one another. None of us, in our private lives or our political constructs, are ever independent.
"The world is changing and needs different institutions, but not just removing ourselves from each other."
Sir Bob said the at times combative nature of the debate over the vote on September 18 was "very upsetting".
He said: "We're down to the thin bones of the argument when people have started shouting at each other. People should be allowed to speak in any forum they like, be listened to and rebutted.
"That's the way we do these things here, because ultimately modern civilisation was invented between these two peoples."
He added: "It's only together, with a single shared sense of purpose, that we get to do things in the 21st century. There's plenty to be done. Let's get on and do it together."