Yes, they do it voluntarily, but in Brin's case that involves voluntarily being insulting and abusive to people and then getting upset if anyone responds in kind.
I don't have an issue with Cam or Frog and don't lose sleep over Brin's behaviour, but as someone who has been on the receiving end of Brin's 'moderation', I'm not going to stand by while he is portrayed as some sort of saint.