Tesco’s former CEO is, as Sunday’s show confirmed, the quintessential working class boy made good. He grew up on a council estate in a pre-fab with a dad who was a part-time greyhound trainer and three brothers who all went straight into apprenticeships at 16.

His choices on his island were unmistakably Northern working class too. Homeward Bound by Simon and Garfunkel was picked, not because of its popularity in the 1960s but because it was written at Widnes railway station. Even when Leahy’s tastes strayed into more refined territory with Pachabel’s Canon in D it was prefaced with the explanation that it was the melody used for Everton’s 1995 Cup Final anthem. Superb.

Leahy’s radio appearance certainly made headlines, but not for his musical choices. Mid-way through the interview host Kirsty Young asked him if he felt sad at the sight of “boarded up little shops on the high street”, forced out of business by Tesco.

Leahy’s answer was a characteristic mix of bluntness and humility. He confessed to some sadness but then pointed out that their extinction was “progress” from a “medieval” approach to one that was superior and more attractive to consumers. No one, as Leahy pointed out, had been forced to shop at Tesco. “You don’t want a society that prevents the one that’s good at getting more customers and doing well,” he explained and then pointed out that Tesco was once a small store too.

His interview scandalised the usual Tesco-haters. Guardian readers, in particular, were hilariously critical of Leahy in the aftermath of the show, with many calling for (yet another) Tesco boycott. Despite this, Leahy was correct. The game he and other marketers play is called capitalism and it rests on simple, predatory logic – weak brands must die and strong brands must kill them. Only then will the consumer be served and the market improve or, to use Leahy’s term, progress.

Unfortunately, many marketers find this sharp end of capitalism unpalatable. We’re happy with the idea of deriving success from “delighting” customers but shy away from the side of that equation in which we “destroy” the competition.

Marketers are, for the most part, a liberal bunch so we confuse sticking up for the underdog with the protection of failure. We are more likely artists than assassins, so we fail to respond to capitalism’s insistent requirement for progress through a mistaken belief in preservation. Tesco destroyed the local butcher because consumers preferred the supermarket’s offer to the crap local butcher. It’s not sad. It’s not unfortunate. It’s capitalism, and it’s how we marketers roll.

One kind of marketing director is the friendly type who wants to grow share without rocking the category too much and comes up with tame, empty statements like “we are our own biggest competitor”. Fuck that. Our biggest competition is the brand crushing us because it’s led by a proper marketer who is wiping us out with a blistering strategy built from a winning combination of hatred and strong marketing.

The only good marketers are the ones who openly and proudly aim at the destruction of their competition, who plot and plan for this moment and who revel in the occasion when it finally occurs. I remember a meeting with my favourite chief executive who interrupted a debate on the impact of a proposed advertising campaign on a competitor’s business with the words “Fuck this. Kill everyone”.

Leahy was more subtle, but his sentiment on Sunday was the same: the weak brands must and should be killed for society to progress. As marketers we are the agents of this destruction. It’s what you signed up for. If all this talk of hate and destruction makes you uncomfortable, become an artist or work for the National Trust. Marketing needs killers.

Leahy does not have to be your guru, pick any of the great marketers and you’ll find that same killer instinct deep within. In Walter Isaacson’s biography of Steve Jobs, the founder of Apple exemplifies the killer spirit when he proclaims he will spend “every penny of Apple’s $40bn in the bank” to destroy Android. “I’m willing to go to thermonuclear war on this” was Job’s chilling summary of his approach to competing with Google in the phone business.

Ryanair boss Michael O’Leary may not be everyone’s cup of tea but he is inarguably the most successful CEO in Europe. He too feels uncomfortable when executives avoid talk of their competition. According to O’Leary this is “all bollocks”. He is clear about his approach to competition at Ryanair: “Everyone wants to kick the shit out of everyone else.”

Leahy. Jobs. O’Leary. All phenomenally successful capitalists and legendary marketers to boot. And all with the unfettered aggression and naked hatred for competition that great marketers share.