Johnston is wrong.
There is plenty to be said for covering all the aspects of racing that don't involve betting. The history of the sport, jockeys, trainers, owners, breeders, studs, stables, pedigrees - all can be covered by TV in interesting ways.
But gambling is an integral part of the sport's appeal. Most people who love the sport are likely to have developed their initial interest via the betting side.
As a racing fan, I can certainly watch and be interested in a race even if I haven't had a bet. But my main interest will be in trying to glean something from it that might help me with my future betting.
And, of course, the main person putting money into the sport, apart from the owner, is the punter.
A racing programme shouldn't be exclusively about gambling - and, despite what Johnston says, they never are - but a racing programme that ignores gambling wouldn't be a racing programme.