Who can blame him?

Andy Murray has considered the likely consequences of making his feelings known about the independence debate and decided he can do without the abuse, thank you very much. He knows only too well how heated it could get. Before the 2006 World Cup, he joked he would be supporting anyone but England, only to have to make clear repeatedly in interviews that he had not been serious.

How that experience would pale in comparison to the likely reaction he would get if he were to pick a side in the referendum debate. The question of Scottish independence has always been highly charged, with the propensity to escalate to sporrans-at-dawn, but as polling day nears, tensions are running higher than ever.

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The Glaswegian comedian Susan Calman, a regular on BBC Radio 4's Newsquiz, was pelted with abusive online messages and death threats last spring after making gentle jokes during the show about the referendum. She was accused of betraying her country and being racist towards her own people. In amazement at the level of aggression, she called for those engaging in the debate to remember their sense of humour.

The incident led fellow Scottish comedian Rory Bremner to call on both sides to "rein in their shock troops". Like Calman, he commented that Scottish politics was "unlike any other area I've done before in that there is a great degree of hostility", but it is very unlikely the temperature will get any cooler in this debate. Over the past month, open enmity has broken out between Scottish Government and UK Cabinet ministers over currency union, the economy and EU membership, making both frontline political figures and grassroots supporters more tetchy than ever. No wonder Murray wants no part of it. Nor does Billy Connolly who has formally declined to declare his preference, announcing he will not vote in the referendum, describing the debate as "a morass that I care not to dip my toe into".

It is questionable what added value celebrity supporters bring to the debate, especially those who are not eligible to vote. Famous figures who attempt to influence voters from their sun-soaked villas or London penthouses are understandably given rather short shrift by many people who live in Scotland. Murray cannot vote on September 18 because he lives in England, which would certainly open him up to more slings and arrows if he did take a side.

Still, it is disheartening anyone should feel afraid to admit their feelings on this crucially important subject for fear of being buried under a torrent of insults. Passion and vision are desirable in the public conversation about independence, but not aggression and name-calling.

Polls show hundreds of thousands of Scots have still not decided which way they are going to vote in September. What they require is reasoned debate on the key issues and the space to weigh up the opposing arguments calmly. Both sides have a duty to provide that - without the abuse.