There's something a bit odd about confessing that you were part of an institutional attempt to cancel a specific person, without naming the person or what their specific concerns were, or what specific institution this was; and also claiming that the reason you regret this now is because they were "harmless" rather than "correct".
Someone who in 2015 was concerned about "authoritarianism in technology" possibly came from a cluster of political perspectives that is relatively close to my own; and also possibly came from a cluster of political perspectives that I am relatively opposed to. It's hard to tell which from just that wording and the fact that someone with institutional power in 2015 wanted to cancel them.
I'm certainly curious for more details about exactly what happened here. I imagine it would compromise your anonymity to say more, and depending on the details it might even be bad for that person.