Over three months, researchers found anti-Semitism, racism and homophobia on platforms, including DLive and Odysee, where users stream and chat about games such as Call of Duty and Minecraft.
"Once you're in that world, then the radicalisation starts to happen," Joe Mulhall, of anti-fascist organisation Hope Not Hate, said.
"That's when you start to go to other meetings, to smaller groups that aren't necessarily playing games, talking about politics more explicitly."
In response, Telegram told BBC News it used a "combination of proactive monitoring of public spaces and user reports" to remove content breaching its terms of service.
Their policies cite zero tolerance against hate and violent extremism and both say they are proactive at removing any content violating guidelines.
Call of Duty said: "The actions we have taken to confront racist behaviour include banning players for racist and hate-oriented names, implementing new technology and making it easier for players to report offensive in-game behaviour."