Nostalgia a New Heresy?

The first of Jonathan Sumption's Reith Lectures went out this morning and, it seemed to me, lived up to expectation. It was lucid, elegantly expressed, thoughtful and incisive, and raised some very pertinent questions about the effects – particularly on our freedoms – of the relentless advance of law to fill the space left by the retreat of politics.
  In the question and answer session that followed, I noted that more than one questioner accused Sumption of being 'nostalgic' for some past time. I've noticed this accusation being made before, notably about Brexit voters and UKIP members, both of whom are supposed to be nostalgic for a mythical past, sometimes identified as the Fifties. Which begs the question, even if this were true, what is wrong with nostalgia? Surely it's a part of the human condition to look back fondly on times that now seem better than these – often the times of our childhood and early years. We all feel at some level the sense of a lost Golden Age which is irrevocably past and can never be recaptured – hence the pain of nostalgia. Nowadays, however, the word 'nostalgia' is becoming an accusatory term in political discourse (or what passes for it). It seems to be a kind of code word (even a 'dog whistle'?) that suggest reactionary views, inability to cope with the present, a tendency to the swivelling eye and the foam-flecked chin. Is 'nostalgia' on its way to becoming a new heresy, a deplorable new 'phobia' (of the present), an unpardonable denial of the narrative of Progress and its unshakable faith that the present can only be better than the past? That will never do.
  Not that Sumption is 'nostalgic' anyway – which made it all the odder that this term was deployed against him.