Alexandria Ocasio-Cortez isn’t left enough for some progressives who think Bernie Sanders shouldn’t be supporting President Biden. How many angels can dance on the head of a pin? How small can the liberal tent get and still win?

It’s the old question in politics and public policy: Unity or purity? Are so-called “purity tests” — whether for progressivism or conservatism — worthwhile, or are they counterproductive and ultimately self-defeating?

The way I see it, as a longtime progressive in the public health space, democracy is more a tender sapling in need of constant care than an immovable oak. Currently, nations worldwide — including the United States — are learning the true fragility of democracy. From the attacks on LGBTQ people to government censorship, freedom is at risk in more ways than one. Freedom-loving people have a wide variety of interests beyond the conventional political process. Freedom haters, conversely, have the single-minded purpose of wiping out fundamental human rights, and their unity in that pursuit gives them power.

Despite often representing a minority of the population, the opponents of freedom tend to win because of their dogmatic commitment to stand as one. They are determined to unite as allies. In contrast, the lovers of freedom often dissipate their energy through infighting, which eventually breeds apathy. Purity tests create frustration, rapidly sending classical liberals running for the exits.

On the progressive side, too many believe that only the purest belong in their movement. The haters keep it simple: If you hate the same people we hate, you’re in.

Consider 2016, when Donald Trump united even skeptical Republicans by railing against common “enemies” — from the mainstream media to what he perceived as the political establishment. In truth, it happens on both sides, with Biden courting initially dubious Democrats during the 2020 primaries by identifying the “MAGA” movement as a common enemy. The Biden campaign is doing the same now, urging unity within his party.

Unity breeds more unity, while division creates more division.

For progressives, why isn’t it enough to coalesce around the common enemy of hate? Once progressives defeat hatred, we can empower each individual or group to pursue their unique agendas according to their priorities and beliefs.

The Black Lives Matter protests in 2020 — inspired by George Floyd’s murder — offer a viable case study in unity, at least when they first took place. The largest sustained civil rights marches in American history welcomed all people who opposed police brutality. But once the protests subsided, the initial unity eventually fractured over purity, creating — in part — a cautionary tale.

LGBTQ Pride presents another case study. Pride events are unifying because every stripe of the rainbow has a place in the line of march. Means of expression vary wildly, but most marchers celebrate diversity and inclusion that uplift us all. There are strong shows of communal unity until one stripe attacks the other instead of strengthening the alliance.

I see the consequences of the ideological purity test in my work. Our advocates, who are working to rid the world of AIDS, are often forced to spend more time fighting supposed allies than those openly hostile to our movement. Needless squabbling over strategies, tactics and funding risks the viability of our movement rather than expanding it for the sake of HIV medical care and prevention everywhere.

Because loud dividers drown out unifiers, unifiers must take a stand. If they don’t, they surrender the movement for freedom and democracy — first to the dividers and then, ultimately, to the haters.

It is fashionable to believe that movements can thrive without leadership. There is a healthy distrust of leaders based on bitter history. Nevertheless, how successful has any movement been without leadership that preaches and practices unity?

The key is holding leadership accountable without attacking leaders at every turn and fueling more division. Those who support unity should be celebrated, not condemned, even if they don’t answer every question right on the purity test. Americans should apply that logic in all political and policy contexts, whether the 2024 election, the push for affordable housing or LGBTQ rights.

These are sobering times in America. Our impulse to debate every issue until exhaustion is a distraction. The natural skepticism of any leader is self-defeating. We desperately need trusted leaders to go head-to-head successfully with the haters. And once we identify them, leaders need to be trusted to lead.

You are either pro-freedom or not. You are either pro-democracy or not. Muddying the waters with unnecessary purity tests only ends up eroding both.