Poor Martin Amis.

It is not enough that his new novel, The Zone Of Interest, is snubbed for the Man Booker longlist when, as the review on these pages suggests, it is an eminently finer work than many on it. Nor is it enough that whenever he is interviewed, half the article is usually devoted to a reprise of his past existence. That this life dates back beyond his birth, to that of his father Kingsley, is predictable, if unfair. What is worse, is that most conversations about Amis adopt the tone used for celebrities or politicians, especially those who have been caught out in some minor, mildly tarnishing scandal. Very few discuss Amis the restless, ambitious, questioning writer, as he deserves.

In the middle of a session at the Edinburgh International Book Festival, I found myself silently defending him against the latest salvo fired his way. The occasion was a discussion with feminist activist and academic Lynne Segal, whose recent book, Out Of Time, offers reflections on ageing, especially as experienced by women. Speaking as if against the clock, Segal castigated Martin Amis for his vision of a future in which "demented oldies" would be roaming our streets.

One can understand why the term might offend her, but her loathing of Amis is less explicable. Yet again, it seems, his black humour has flown over the heads of those looking to take umbrage. Amis, of course, does not need anyone to defend him. As Segal lectured her audience, I pictured the author sitting on the platform beside her, a model of urbanity, amusement and provocation. One suspects even his Chelsea boots would annoy her.

Amis was not Segal's only literary target. Philip Roth came in for an even more severe beating, as she sneered that all his novels of the past 25 years have been about "lecherous mavericks", obsessed with their declining sexual powers. Were Roth to share a stage with Segal conflagration would be assured. I would rather face a firing squad than Roth's contempt, but I was outraged at Segal's glib dismissal of his oeuvre, especially since his golden period began with American Pastoral in 1997. This late resurgence was astounding, and could not have been achieved by anyone who had not reached advanced middle age, and the wisdom that comes with it.

That Segal's depiction of Roth's later novels was inaccurate and crude is bad enough. But surely, in a truly feminist world, in which one hopes that sexuality would be discussed by men as well as women, there is nothing amiss with a lament for the physical effects of age? Or are we to believe only women are entitled to discuss their withering physique in fiction? As we get older, are we all to take the position that Segal told us Germaine Greer had reached, of being relieved sex is over and done with? And even if some of us no doubt are, why should others not be allowed their say? In other circumstances, Roth's regret for a diminished libido would be applauded for its rigorous realism.

In the end, however, all of this is trivial. The real issue in this context is far more important than that of gender sniping. The point is whether a novelist, whoever it may be, feels free to write about whatever he or she likes, and can do so well. Looking at publishers' lists, two things are evident. One is there are as many emotionally dishonest or misleading novels as when Barbara Cartland and John Creasey were in their pomp. The other is that, despite this, there is a growing school of first-class fiction by men challenging dated notions of what is appropriate for them to write about.

Writers far younger than Roth and Amis are taking their cue, or given courage, by their naked revelations and disregard for public opinion. In so doing they are staking out their own territory, much of it domestic, or emotional, or sexually frank, and thereby broadening the scope of literature. Surely even Segal must be glad this is so?