Substack faced further criticism in November 2023 for allowing its platform to be used by white nationalists, Nazis, and antisemites.[61] In an open letter, more than 100 Substack creators threatened to leave the platform[62] and implored Substack's leadership to stop giving bigotry a platform.[63] In response, Substack co-founder Hamish McKenzie said the company would continue to allow the publication of extremist views because attempting to censor them would make the problem worse.[11][64]

From their Wikipedia page https://en.wikipedia.org/wiki/Substack