Deplatforming has been shown to have worked to reduce the influence of extremists, specifically those that incite violence https://www.vice.com/en/article/bjbp9d/do-social-media-bans-....

It doesn’t need to work perfectly for it to be useful.

Btw do you know what doesn’t work? Appeasement. That only lets bad actors know that they can go even further. Resisting taking reasonable action for fear of violence is plain old appeasement.