Was there ever a well-documented, widely accepted to be *false*, accusation of genocide?

https://en.wikipedia.org/wiki/Great_Replacement_conspiracy_theory

https://en.wikipedia.org/wiki/Allegations_of_genocide_in_Donbas

White genocide conspiracy theory (South Africa)

See also: South African farm attacks and Land reform in South Africa

And: US Accepts Only White Refugees For Sixth Consecutive Month

I don't have an example for you. I see another left hook coming your way unexpectedly and that is from the term "genocide." It's fairly new. It was coined during WW2. And people still argue about the definition. We have killed each other for time immemorial but we didn't have that label that stuck to slap onto the most egregious cases. So anything before the Holocaust is given the label after the fact. And that will have some historians at the ready contesting it. So most genocides are contested not because they don't want to admit a lot of killing was going on. But because they cannot agree on what genocide means.

They hold ten-year trials in The Hague to figure out if a Milosevic or similar asshole is guilty of it. There is wiggle room in the definition. Were enough people killed? Was it targeted enough? And other distasteful questions.

We talk about genocide like it's a fixed term and everybody knows what it means. But it's more in that "I know it when I see it" category and the resulting wiggle room will make any argument you're having harder. You can't get to the slam dunk of your argument when your opponent withdraws from it on this technicality.

White genocide?

Of course. The Nazis accused Jews of committing genocide against white people. That's why the 14 words are a thing, "We must secure the existence of our people and a future for white children," the implication that "the existence of our people" is under threat. It's the same reason modern facists chant, "Jews will not replace us." Nazis (not just the modern ones, but the OG ones) promoted conspiracy theories that Jews were trying to make white people become gay/trans to prevent them from reproducing, and communism was supposedly another Jewish plot to make white people too soft and tolerant to use force against Jews. And naturally, interracial marriages were another form of "genocide," as they diluted the racial purity of of the Aryan race.

I have used the argument in the past, “If given all available evidence you’re still not sure a genocide is happening, you can probably safely assume that it is, because humans just constantly do genocide.”

That's a bad argument regardless, because the default position on any claim or accusation should always be skepticism. The burden of proof is on the person making the claim. Some people seem to have gotten it into their heads that accusations of genocide are an exception to that, somehow.

Generally, historical genocides such as the Holocaust are incredibly well-documented, and the term "genocide denier" is meant to apply in such cases. There is nothing morally wrong with denying a genocide that doesn't have the same kind of evidence backing it up, that's just called due diligence.

If we want to go into technicalities:

The internationally accepted definition of what constitutes a genocide is quite limited and certainly not identical to what is colloquially interpreted as genocide. The same way murder is distinct from manslaughter.

Serbia was found not guilty of committing genocide by the ICJ in the Yugoslav wars for instance. Serbia did commit various crimes against humanity and ethnic cleansing (primarily by way of deportation) but this was not found to be genocide.

Most scholars believe genocide (as defined under the Genocide Convention) refers exclusively the "physical-biological destruction of a protected group".

Just look at a couple excerpts from this article: https://en.wikipedia.org/wiki/Bosnian_genocide

In the case of Prosecutor v. Krstić (2 August 2001), the ICTY ruled "customary international law limits the definition of genocide to those acts seeking the physical or biological destruction of all or part of the group. Hence, an enterprise attacking only the cultural or sociological characteristics of a human group in order to annihilate these elements which give to that group its own identity distinct from the rest of the community would not fall under the definition of genocide".

On 14 January 2000, the ICTY ruled in the Prosecutor v. Kupreškić and Others case that the Lašva Valley ethnic cleansing campaign in order to expel the Bosnian Muslim population from the region was persecution, not genocide per se.

Though under some nation's law, such as Germany, the definition of genocide is more broad:

However, the ECHR highlighted that the German court's ruling, based upon German domestic law, had interpreted the crime of genocide more broadly than and in a manner since rejected by international courts.[52] Under the wider definition that the German judiciary upheld, the ethnic cleansing carried out by Jorgić was a genocide because it was an intent to destroy the group as a social unit, and although the majority of scholars took the view that German genocide law should interpret genocide as the physical-biological destruction of the protected group, "a considerable number of scholars were of the opinion that the notion of destruction of a group as such, in its literal meaning, was wider than a physical-biological extermination and also encompassed the destruction of a group as a social unit"

Tl;dr: It's only genocide when it comes from the genocide region, else it's just sparkling ethnic cleansing.

This doesn't count as an answer to your question because aside from convincing 21st century whites living in first world countries, it's kind of a hard thing to pull off.

But similarly, did you know there's never been a act of geopolitical aggression that hasn't employed the use of a variant of the Black Legend? Think about it.

"The Jews were invading and subverting our governments because they have no homeland"

"Native Americans eat people, we HAVE to colonize them"

"The Moors are invading Spain, if we don't retake the holy land they'll never stop pushing us out of our homes"

"The Chinese will never grow up to be big and strong unless they buy enough opium"

"Gazans are a threat to the state of Israel, their religion is incompatible with us"

Kind of crazy to think that for a tactic as old as the human race, it never really gets called out when people in modern day just say it with their whole mouth.

The closest example I can think of is controversial. Trump has stated that there is a Christian genocide going on in Nigeria. Credible human rights organizations have said that it is terrorism and no single religious group is being targeted. I really don't know if genocide is the correct label as plenty of Muslims and others have been killed too. Or really whether it could even be considered genocide as Christianity isn't an ethnicity but people ARE dying.

Some zionist claimed that october7 was genocidal

On a global scale, with buy in from multiple international human rights and aid organizations? No. Once you reach enough global critical mass of agrement, it's not a false accusation almost by definition.

It has been and is currently the case, that some local governments or groups falsely push a genocide narrative for their own benefit. That does happen. When it does, you never find anyone outside said group that truly believes it.

Genocide vs non-genocide designations are all political. Some are fairly unanimous. There are many categorically absurd ones, but extreme evil/idiocy on Lemme supports many of them. US empire narratives deny real ones, and are responsible for fabricating the most recent examples.