The day after Pete Buttigieg won Iowa, the writer Mark Harris, who is married to the playwright Tony Kushner, tweeted: “Even if you support someone else, as I do, the fact that a gay man can win a state caucus for President is a welcome milestone.”

Iowa has long been something of an outlier – in 2004 it was among the few Republican controlled states that rejected a constitutional amendment banning same-sex marriage – but the idea that an openly gay man could win the Democratic caucus there took most Americans by surprise. That it was a milestone, as Harris pointed out, was clear – or should have been. The fact that it needed stating said everything about this strange, emotional, deeply divided campaign.

Like me, Harris is a Gen Xer who can remember the Reagan-Thatcher years, and who witnessed a new identity politics emerge from the devastation of Aids. Many of those people saw friends cut down in the prime of life. They went to paupers’ funerals for colleagues long abandoned by their parents. They witnessed a criminal and deadly silence from Washington, compounded by snarky jokes about a “gay plague”. In the UK, when I was at college, gay men were still being arrested for kissing in public. We had to wait until we were five years older than our straight counterparts to have sex.

For those among us who can recall a not-too-distant time when going into a gay bar still felt dangerous, watching a gay presidential candidate get so far while being mercilessly pilloried has been a disorienting experience. It was as if our own community was clipping our wings at the very moment we were learning to fly.

It was as if our own community was clipping our wings at the very moment we were learning to fly

Buttigieg did not deserve unconditional support – no one does – and in debates he had to stand on his record, as all candidates must. Allegations that he’d sided with white police officers over the firing of South Bend’s first black police chief, and that the city’s economic growth had bypassed black communities, stuck hard. When he abandoned the race on Sunday it was a tacit recognition that in spite of his ambitious Douglass Plan, a manifesto for black empowerment, he had not swayed minds. His lack of traction with black voters, though in the end about the same as for Elizabeth Warren, remained his achilles heel to the end.

Yet whatever critics thoughts of his record in South Bend, much of the conversation was colored by lurid characterizations of the way he chose to present his gay identity.

Early in the campaign, a Slate columnist characterized Buttigieg as having “sturdy ties to straight culture”, whatever that means. Then, last July, the New Republic published, then deleted, an essay by the novelist Dale Peck which excoriated Buttigieg as “not the same kind of gay” as Peck, and by implication many other gay men. The piece was widely condemned, but it also presaged what has become a commonplace meme on political Twitter: Buttigieg as a gay Uncle Tom whose success merely reflects his servility to the status quo.

Although there was widespread outrage when rightwing pundit Rush Limbaugh claimed that a gay man who kissed his husband onstage could not win the presidency, it is, perversely, on the left that this kind of critique has flourished. Some of that reflects the trajectory of a movement that has become an ever-expanding umbrella for marginalized communities. Although a white gay man, Matthew Shepard, remains an enduring symbol of homophobic violence, the greater challenges faced by people of color and transgender women of color in particular now preoccupies the LGBTQ+ movement, and rightly so. In a society where a show such as Modern Family can be ABC’s longest-running comedy series, a married gay man – though impossible a scant five years ago – increasingly seems pedestrian or even bourgeois. In that frame, Buttigieg’s military background and expression of faith read as simulacra of straight culture. Buttigieg’s centrist emphasis on bringing the country together also struck the wrong chord. In the algorithmic Twitter ghetto in which many Buttigieg detractors live, that kind of talk just sounds like more of the same.

We tell ourselves that politics is a line from left to right, or vice-versa, but lately you’d be forgiven for wondering if it’s not, after all, a circle: in 2016 some Sanders supporters, in a grotesque echo of Donald Trump’s rallies, chanted “lock her up” at the mention of Hillary Clinton. Buttigieg, who supports reparations for descendants of enslaved people, scrapping the electoral college, and has an aggressive plan to make the US carbon neutral, is dismissed as a neoliberal barely distinguishable from the president.

For those with long memories, that kind of lazy generalization is troublesome. In 2000, people were similarly dismissive of Al Gore when he was running against George W Bush. Instead, many on the left voted for the third-party candidate Ralph Nader, who received almost 100,000 votes in Florida, helping to hand that contested state to Bush by a whisker, and with it the presidency. It’s important to hold candidates to high standards, but purity contests can backfire in unintended ways.