In the six-or-so years I’ve been doing broadcast radio commentary, I have never laughed out loud on air. Until Saturday.

On BBC Radio Scotland’s weekend edition of Good Morning Scotland, I appeared alongside Kevin Pringle, Alex Salmond’s former right-hand-man in the Scottish Government and former head of communications for the SNP; the same job I performed in the early part of this century for the Scottish Conservatives.

Kevin and I do media together regularly. He’s fairly rare, as a nationalist who is able to analyse with balance and impartiality whilst retaining his constitutional beliefs and his party membership. I am, I suppose, even rarer, as a former Tory who has become a non-member, floating voter, sceptic of political parties and someone with relative openness to Scotland’s constitutional future, albeit with a fixed belief in social and economic liberalism.

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On this occasion the discussion was about party election strategy, on a day which ended with a degree more certainty, courtesy of the SNP and the LibDems, that we would indeed be enjoying a December election. But I was not laughing at Kevin. For there was a third participant in this discussion - James Mills, a former adviser to Jeremy Corbyn and John McDonnell.

James’ first intervention in the discussion was to excoriate Jim Cusick, an experienced lobby journalist formerly of the Independent, the Sunday Times and the BBC. Immediately before the discussion between James, Kevin and I, Jim provided an analysis which included the internal misgivings inside Labour about Corbyn’s fitness for office. It was a highly partisan response to a highly non-partisan analysis.

Now, I should clarify that I am not proud of myself for chuckling, and I did not do so out of any malice towards James. He’s a highly politically motivated person, which is to be admired, as well as a husband and a father, which is to be admired more. Really I was laughing ironically at myself, because James’ intervention cemented in my head a concern I have harboured for some time: that recent referendums have served to obliterate the lines which previously existed between journalists, commentators and activists.

Firstly, it is important to understand what should be the difference between those three types of participant. The role of the journalist is, to put it simplistically, to inform viewers, listeners and readers of what they understand to be happening. This may not always be perfectly balanced, depending on the focus of the topic. And, indeed, I do not expect the contribution of journalists to be impartial, either, because their publications are not. So we might expect the interpretation of, say, a Guardian journalist to a piece of breaking news on Brexit to be different than that of, say, a Telegraph journalist. The expectation, though, would be that a journalist would happily turn their hand to any story irrespective of whom it involved; Brexiter or Remainer, Unionist or Nationalist, and so on.

There is a key test, here and it is this: as a consumer of the news that they produce, I should not know how a journalist votes, whether in elections or referendums. That is the crucial difference between a journalist and a commentator. As soon as it becomes clear how they vote, they have ceased to become a journalist and bled into the commentary.

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In this, I must say, I think that Peter Oborne’s criticism of a couple of particular journalists - the BBC’s Laura Kuenssberg and ITV’s Robert Peston - was wrong. His insinuation that they effectively swallow lies from Downing Street is off-the-mark because their job as journalists is to report what they are hearing from politicians and campaigns, whether that be Downing Street or the opposition. Both of those individuals fit my description of journalists rather well.

However, not all of their colleagues fit it, with too many having morphed into being partisan commentators. Those of us observing the media in Scotland would have been able to see this coming since 2014. Referendums, as we all now know, are destructive things. They divide families, workplaces and society. And in the highly charged political environment they produce, the integration of journalism and commentary has gone almost unnoticed.

It is now commonplace in the pages of national newspapers to see print and broadcast journalists giving us their opinion, rather than simply their analysis (the nuance is critical), in a first-person column.

That journey - from journalist to commentator - is often mirrored at the other end of the spectrum as commentators morph into activists. It is here where we can return to the example of Saturday’s radio debate. Commentators are very commonly people who have a political history. This rather goes with the territory - anyone with enough interest in the detail of politics to qualify as a commentator has probably been around a political party in their past.

There is no wrongdoing in the audience knowing what a commentator’s opinions and voting patterns are, but they are entitled to expect that he or she will be able to offer a semi-detached perspective on the story. They should be able to go beyond the spin and tell the audience what sits behind it, analysing its potential effects in a thoughtful and, importantly, unemotional way.

But just as there is a critical difference between a journalist and a commentator, the same difference exists between a good commentator and an activist. Emotional, blinkered, one-sided interpretations which show an inability to understand another perspective are a sign that you are consuming the views of an activist rather than a commentator. On Saturday, it was clear that Kevin and I fitted into the box of commentator, whereas James (and I am sure he would himself accept this) is clearly an activist.

I know that this might not seem important. But it is, now more than ever. This blurring of the distinction between journalists, commentators and activists goes right to the heart of public trust. Now more than ever, we are dependent on the media to help the public in the navigation of the most divisive issue in our collective political memories.

For me, broadcast and print media get a "must try harder" mark. They need to understand who they are commissioning, and why. They must decide before they pick up the phone what they want their panel to be - journalism, commentary, or activism. All are legitimate, but all are different and should not be mixed.

Modern politics is corrosive enough; let’s not make it worse in the media. The people need to know who is talking to them.

Andy Maciver is Director of Message Matters