"Hail Trump, hail our people, hail victory!" Spencer shouted in the video released by The Atlantic, shot at an event in Washington DC on Saturday.
Speaking to The New York Times on Tuesday, the President-elect repudiated the fringe group, saying he did not want to "energise" them. "I condemn them. I disavow, and I condemn," he was quoted as saying.
Paul Joseph Watson, editor-at-large of PrisonPlanet, the sister site of Alex Jones' InfoWars, took to Twitter to speculate that Spencer was "a Fed like Hal Turner", referring to a notorious white nationalist and Holocaust denier who was revealed to be an FBI informant in 2008.
In a separate post, he said there were now "two 'alt-rights'". "One is more accurately described as the New Right. These people like to wear MAGA hats, create memes and have fun," he wrote.
"They include whites, blacks, Asians, Latinos, gays and everyone else. These are the people who helped Trump win the election.
"The other faction likes to fester in dark corners of sub-reddits and obsess about Jews, racial superiority and Adolf Hitler. This is a tiny fringe minority. They had no impact on the election. Guess which faction the media is giving all the attention to?"
Cernovich, a prominent Trump supporter, described Spencer as "the media's dancing monkey", and speculated that he was "controlled opposition".
"The Atlantic (and perhaps the CIA) is building up Richard's brand, giving him millions in free PR," he wrote. "The fake news media ties Richard to Trump. In exchange for these goodies, Richard throws up a HH."
After being attacked by some of his followers, he distanced himself further, describing the "Roman salute" as an "unimaginable folly and a sure-fire way to destroy your movement". "I'm not alt-right, there's no movement that can kick me out. I do my own thing," he tweeted.
Speaking to the BBC last month, Yiannopoulos described the alt-right as a "new movement full of energy and enthusiasm and excitement".
"It's primarily concerned with the three things energising Trump voters: immigration, trade and political correctness and free speech generally," he said.
"You can define it very broadly to include classical liberals, disaffected leftists, ordinary conservatives, and this new, young, very energised, kind of troll-y, mischievous, youthful contingent that has suddenly become interested in politics again.
"That's the wing I'm most closely associated with, and that's the most exciting bit because it's the bit that had checked out of politics almost for generations.
"Donald Trump has re-energised those people by standing up to the nannies, the cultural scolds, the bullies, the feminists, the people who don't want you to say things, the people who are always talking about offence-taking."
But following the Spencer incident, even some on Reddit's 300,000-strong Donald Trump fan community, r/The_Donald, began to call for the "alt-right" tag to be abandoned.
"I used to think I was alt-right," wrote FricasseeingRabbit. "But after doing some research the racists definitely had the label before just generic Trump fans did. Let them have it. Alt-right means white national socialist and that's fine with me."
User JackandFred wrote: "It's really unfortunate that people who seem to think racism or Nazi ideals have now become mainstream because they think that the alt-right's new popularity has anything to do with them."
Secretlyacutekitten added: "Same, not any label apart from an American that supports Trump. Alt-right was introduced to me by Clinton where she was ranting at a frog. Knew then it was a complete smear job."
