Iran’s merciless persecution of Nazanin Zaghari‑Ratcliffe, the Iranian-British woman held in Tehran’s Evin prison on spurious charges of spying, is deeply disturbing. What possible purpose was served by the airing this week on state television of a video showing her arrest in April 2016, as she prepared to board a plane to London?

When accosted by security men, Zaghari-Ratcliffe does not for a moment act guilty. She is not concealing anything. She does not try to run away. She looked then like the person she still is today: frightened, alarmed, uncomprehending and, above all, innocent. Showing this video was the regime’s latest, pathetic effort to justify the unjustifiable.

Zaghari-Ratcliffe is not alone, figuratively at least. Her incarceration is part of Iran’s wider war on women’s rights – a war waged with fluctuating intensity by the exclusively male clerical establishment since the 1979 revolution, using legalised gender discrimination, fear and brute force.

What of Nasrin Sotoudeh, for example, the valiant human rights lawyer awarded Europe’s 2012 Sakharov prize while locked inside Evin? Sotoudeh helped defend women arrested for defying rules on the wearing of hijab in public, some of whom were attacked with acid. She was jailed again last year and began a hunger strike in November.

Or what of Narges Mohammadi, with whom Zaghari‑Ratcliffe also intends to stage a hunger strike inside Evin, beginning on Monday? Mohammadi, originally jailed for “propaganda against the state”, was handed an additional 16-year term in May for campaigning to abolish the death penalty. Like Zaghari‑Ratcliffe, her health has deteriorated and she has been denied adequate medical treatment.

Their fate, and that of uncounted other activists, female and male, is uncertain. The regime’s ultra-harsh treatment of dissent breaches Iran’s own laws and its legal obligations under UN covenants. Human Rights Watch reported last month that a crackdown on independent lawyers is escalating. “Now Iran is not only arresting dissidents, human rights defenders and labour leaders, but their lawyers as well,” it said.

What the Zaghari-Ratcliffe scandal, and cases involving Iranian nationals such as Sotoudeh, have vividly demonstrated is the willingness of hardline clerics to use any means, however immoral and unjust, to validate their belief that the Islamic Republic is besieged by malevolent western governments scheming counter-revolution.

What this unrepresentative yet powerful minority fails to grasp is that they themselves, not women’s rights campaigners or states such as Britain, are the real threat to Iran’s security, prosperity and independence alongside the US.

The systemic abuses endured by Zaghari-Ratcliffe confirm all the worst prejudices and stereotypes about Iran peddled by enemies in the Arab Gulf states, Israel and Washington. They invite ostracism and reciprocal bigotry. They open the way to greater violence.

It’s plain that the supreme leader, Ayatollah Ali Khamenei, though old, ailing and underqualified, still casts a reactionary shadow over the regime’s external dealings

Every time Donald Trump traduces Iran’s government as the world’s leading sponsor of terrorism and urges its people to revolt, somebody, somewhere will think of Zaghari‑Ratcliffe or the many other innocents languishing in Iran’s jails, and conclude the US is right to go after the mullahs. Every time the EU defends the breakthrough 2015 nuclear pact against American opposition, the more once supportive western politicians dismayed by regime abuses will question the strategy.

The more the public hears of the suffering of those terrorised and tortured in Tehran, the more they may question the policy of engagement, supporting instead a policy of attrition. Sadly, a showdown with the Great Satan and chums is exactly what some hardliners want. If for no other reason, such a catastrophe should be resisted by all means.

The real danger Iran now faces emanates not from people such as Zaghari‑Ratcliffe, or the BBC, or even from those within Iran who seek reform, a freer society and a more open politics. It comes from the west’s own fundamentalists: people such as the Iraq war-hawk John Bolton, Trump’s national security adviser; Benjamin Netanyahu, Israel’s bellicose premier; and the Saudi crown prince, Mohammed bin Salman. And who in Tehran would give the west’s hardliners the justification they seek to foment regime change? Answer: the very same people whose personal ambition, nationalist rhetoric and heedless cruelty leads them to penalise the likes of Zaghari-Ratcliffe.

It’s hard to penetrate the clouds of Tehran’s factional rivalries. But it seems clear that Hassan Rouhani, Iran’s twice‑elected president, the foreign minister Javad Zarif, and like‑minded centrists and “moderates”, are on the back foot – their tentative western outreach torpedoed by American bad faith and sanctions.

It’s plain too that the supreme leader, Ayatollah Ali Khamenei, though old, ailing and underqualified, still casts a reactionary shadow over the regime’s external dealings. It’s unarguably the case that the Revolutionary Guard Corps, personified by the Quds Force general, Qassem Suleimani, wields enhanced influence, in part due to its success in Syria.

But it is also evident that Sadegh Amoli Larijani, head of Iran’s powerful judiciary, protege and confidant of Khamenei, and younger brother of the speaker of parliament, is among those principally responsible for Iran’s regressive slide into confrontation. Last week he moved closer to the top of the pile, taking the chairmanship of the expediency council, which advises the supreme leader.

An arch-conservative, Larijani is escalating a self‑interested battle with the west. He recently portentously declared Iran to be surrounded by “enemies outside the borders”. He maintains close ties with the security and intelligence agencies. And it is he, more than any other, who controls the fate of Zaghari‑Ratcliffe and other judicial victims, as he showed last month when he dismissed the concerns of Jeremy Hunt, Britain’s foreign secretary.

Iran needs saving from men such as Larijani, just as Zaghari-Ratcliffe needs saving from Iran. But, for all our sakes, it is up to Iranians to make the change, calmly, in their own fashion and without outside interference. Let’s hope they act with urgency.

• Simon Tisdall is a foreign affairs commentator