There's a case for viewing commercial public relations as the 'acceptable face of capitalism'. Championing an organisation's responsibilities to all its stakeholders balances the pressure always to put shareholders and profits first. Corporate Social Responsibility and environmental statements play their part in this.
Contrast this with party political public relations where there is a long tradition from Bernard Ingham to Damian McBride via Alastair Campbell of the PR adviser as chief 'attack dog' for his (my examples are all male) political boss. The unacceptable face, if you like, of public relations.
Why such a contrast between the corporate and political worlds? David Starkey, I imagine, would talk in terms of courtiers and princes. The political PR adviser is a courtier whose power comes solely from their close proximity to the prince, hence the need to take risks and retain the favour of the ruler. Call this the Machiavelli theory.
Politicians, in a democracy, stand or fall by their electoral success. So successful politicians tend to be an everyman (or woman) causing least offense to the electorate (and the Daily Mail). Maintaining an inoffensive public persona requires some strong arm tactics behind the scenes and (unelected) courtiers are more expendable than political princes.
Private sector bosses do not have this pressure to stand for election; they are undoubted kings of their courts. Yet they know they are accountable: to shareholders for profits, to employees for strategic leadership, to customers, regulators and communities. These various accountabilities need careful balancing, the role of corporate public relations.