Homophobia is not only the property of conservatives, nor does it always have a gay target. On Tuesday night, Stephen Colbert proclaimed that the only thing President Donald Trump's "mouth is good for is being Vladimir Putin's c — holster," to raucous laughter from his progressive audience. The joke was about as funny as it was original: For months, Trump's "love affair" with Putin has been celebrated in murals, erotic fiction and photography. These jokes all appear to come from a progressive, anti-Trump perspective, with the intention of criticizing the president for his Russian connections.

Comedy is an effective means of protesting the new administration. But these particular jokes rest on homophobic assumptions. The supposed humor in sexual jokes about Trump and Putin lie in the jokes', well . . . gayness. Suggesting that two putative straight men might be romantically or sexually involved is extra funny: It emasculates them, subjecting them to ridicule and derision. Imagine if Colbert suggested that another Putin ally, Marine Le Pen, is good only for sexual acts, or joked about a romance between Trump and Le Pen: Such jokes would likely be (rightly) criticized as both misogynistic and humorless.

Of course, these homophobic jokes are themselves somewhat misogynistic. Trump is the butt of Colbert's joke because he is the one performing oral sex on Putin, rather than the other way around. The indignity Trump suffers comes from being feminized, from assuming the role that a woman usually fills. Indeed, this is why many scholars and (more recently) courts have suggested that homophobia is rooted in sex discrimination: From an anti-gay perspective, by playing this "passive" role, a gay man betrays his place in the gender hierarchy by doing what a woman should do. Being assigned the female role means that Trump is incompetent, powerless and controlled by Putin.

Some might claim that the humor lies not in insinuating the two presidents' homosexuality, but rather in their reaction to our insinuation. We can imagine that both of these men, who emphasize their machismo and who are no friends to the LGBT community, would object to being called gay. So what we're laughing at is not the joke itself, but their imagined reaction to it. Rather than being homophobic ourselves, we're laughing at the unenlightened homophobia of the jokes' targets.

It's difficult to take that defense at face value: The same behaviors that are deemed acceptable for gay men become the subject of nervous giggles and humorous discomfort when it comes to straight men, even among progressives who are otherwise fully supportive of gay relationships. Unless one fully identifies as gay, being even just a little too intimate with another guy as a straight dude raises eyebrows.

But to take defenders at their word - homophobia, even of the ironic variety, can be harmful. To those less enlightened than the progressive jokesters and their audiences, this brand of humor sends the message that gay jokes are a perfectly acceptable way to undermine a man's social status. It teaches kids that making gay jokes about classmates who are a little too friendly is all right. It tells conservatives and Trump supporters that gay jokes are funny - and that being gay is, indeed, being weak.

None of this is to claim that Trump has been a friend to the LGBT community. In February, the president rescinded guidance on transgender students. In March, he undermined protections for LGBT workers and ditched plans to collect data on LGBT individuals in the 2020 Census. And in April, he installed Neil M. Gorsuch, a judge who models himself after the anti-gay Antonin Scalia, on the Supreme Court.

But using gay love or gay sexuality as a punchline to advance critiques of Trump's policies ultimately threatens to do more harm than good. These jokes take many gay individuals back to less happy times, when humor like this was a reminder of a real and ever-present threat. Such behavior can harm straight and gay kids alike. A close friendship I had with a friend (who turned out straight) when I was 15 ended because his classmates deemed our conversations - about art, music and family - a little too fey to be acceptable. We got off lightly; as anyone who saw the movie "Moonlight" knows, many have suffered far worse. Progressives shouldn't reinforce rhetorical habits that harm gay people, even if their intent isn't malicious.

After all, there is no need for all the gay jokes. The Trump administration has provided talk show hosts and comedians with enough material to last several presidencies. Progressives like Colbert shouldn't have to think too hard to come up with humor that doesn't put vulnerable people down for laughs.

- Konnoth lectures in law and bioethics at Penn Law and NYU Medical Schools and writes on sexuality and the law and health law, and is a former deputy solicitor general for the State of California.