Searching for “did the Holocaust happen?” returned a top result that claimed it did not, as Guardian journalist Carole Cadwalladr reported.
Now, the ranking has changed for US users.
The page – from white supremacist site Stormfront – remains top in the UK.
“This is a really challenging problem, and something we’re thinking deeply about in terms of how we can do a better job,” said a Google spokesman.
“Search is a reflection of the content that exists on the web.
“The fact that hate sites may appear in search results in no way means that Google endorses these views.”
Regarding the recent change in rankings on the Holocaust query, editor of news site Search Engine Land Danny Sullivan, believes this was due to external parties’ attempts to influence the ordering of results.
Mr Sullivan met Google executives and engineers last week to discuss the issue of questionable result ranking, which also affects other queries about, for example, ethnic minorities.
“I’m as horrified and disappointed by the results as many people are,” he told the BBC.
However, he said Google – which processes five billion searches a day – was keen to come up with a solution that was broadly applicable across all searches, rather than just those that have been noticed by users.
“It’s very easy to take a search here and there and demand Google change something,” explained Mr Sullivan, “and then the next day you find a different search and say, ‘why didn’t you fix that?’ ”
Ms Cadwalladr has accused Google of disseminating “hate speech”.
Other result rankings that she questioned include those for “are women evil?” and “are muslims bad?”.
The BBC has also found that some additional queries, including ones without negative terms, also produce controversial answers.
For example, searching for “are black people smart?” in the UK returns a “featured snippet” at the top of the results that claims “black people are significantly less intelligent than all other races”.
“Absolutely they should face scrutiny because they occupy this position of immense power – they mediate a vast amount of the world’s digital information,” he told the BBC.
“I don’t think it’s good enough to just point to their algorithms and say, ‘Well, this is the most popular, this gets the most clicks’.”
As for tackling the proliferation of hate speech, Prof Graham pointed out that many countries around the world have guidelines over what is and is not acceptable – guidelines that Google could, potentially, adopt.
“They don’t have to build those ideas from scratch,” he said.