Every literary festival needs a good row. Normally, they flare up thanks to the invited rather than the uninvited guests. But this year’s Hay-on-Wye Festival, which continues on the Welsh borders until next weekend, has felt a chill spectre pass over its annual feast. Its director, Peter Florence, who from small beginnings in 1987 has transformed the Hay brand into a glittering international franchise with offshoots from Colombia to Lebanon, this year refused to give a platform to David Goodhart.

The British Dream, a study of mass migration and its social effects by the director of the Demos think-tank, has picked up more attention than almost any other work of non-fiction published this spring. Kenan Malik, whose own critical stance on official multiculturalism has influenced Goodhart, wrote in a balanced and fairly sympathetic review for The Independent that “Goodhart raises important questions.”

By any yardstick, this book counts in British policy debate. A shoo-in for Hay, then? Not for Florence, who disagrees with Goodhart’s critique and dislikes his “predictable and sensationalist” book. Hence the absence of any solicitation in the Goodhart inbox. Goodhart has struck back by suggesting that Hay prefers cosy consensus to any serious challenge to liberal orthodoxy.

There are almost more ironies here than sheep on the wet, green hills of Powys. First, The Telegraph – daily home of fulminating punditry about the alleged silencing of critics of mass migration – now sponsors Hay. Next, the past few days have seen festival discussions with global tax avoider Eric Schmidt of Google, with ex-MI5 head and hardline security hawk Stella Rimington, and with former BP chieftain John Browne, whose drastic cost-cutting at the oil giant led to accusations of his ultimate responsibility for the Deepwater Horizon blow-out. Florence himself has just interviewed Jack Straw, populist hard man of New Labour. In this company, Goodhart looks like a dripping lefty.

Beyond the evidence of double standards, or directorial caprice, lurks another issue. Why do literary festivals select and schedule authors? In general, the tail of publishers’ hype wags the festival dog. Most authors appear, unpaid or underpaid, because they have new books to sell. Very few organisers in Britain dare to start with urgent themes and topics, and then find the voices who can best address them.

Snip the intravenous drip that ties festival programmes to the life-sustaining fluid of sales and you might end up with fewer, but more passionate, events. Let’s begin with today’s big ideas, not this season’s catalogue. Now there’s a heretical proposal.