Of course parts of the NHS offer a second-rate service.
If you doubt this, have a look at the front page of yesterday's Leicester Mercury:
Two elderly women were let down by the NHS in the care they received up until their deaths."Second-rate" appears something of a euphemism here.
Today, we reveal that staff are facing disciplinary action following the treatment of 72-year-old Sylvia Densham, who died of infected bed sores while waiting for a hip replacement operation.
Leicester City NHS Community Health Service has admitted failings.
In another case, the health ombudsman has found that 92-year-old Joan Adams, who died from internal bleeding four weeks after being admitted to hospital, suffered more discomfort and distress during the last weeks of her life than was necessary because of "service failure".
Following the inquest into Mrs Densham's death, Leicester coroner Catherine Mason wrote to the Community Health Service listing her concerns over the treatment she had received.
What is also telling is Labour's reaction to Cameron's interview. John Healey, one of the more able figures in the shadow cabinet, is quoted by the Daily Telegraph, as calling the prime minister's remarks "an insult to millions of NHS staff".
This is a thoroughly modern reaction: what matters is not whether something is true but whether it might cause offence to someone.
More than that, Healey's implication that the only factor that determines the quality of care received is the efforts of staff is strange. A socialist, of all people, should understand that workers can be doing their best but be poorly managed or resourced.
Besides, amongst "millions of NHS staff" there are bound to be some who are not doing their best.
The government's NHS reforms look rushed to me. But the direction of travel - making NHS services more responsive to individual and local circumstances - is one that Liberals should support.