I truly do not care about threats to speech that don’t come from government or, in some cases, employers. The problem is the signatories don’t practice what they preach - JKR’s hateful comments, eg, aren’t civil and she’s not owed debate on her terms by the people she scorns. https://twitter.com/heerjeet/status/1281627145991671809
Julian Edelman showed the power of dialogue when he condemned the words DeSean Jackson posted while holding out belief Jackson could be educated on antisemitism. He didn’t write a bratty letter about it, he just showed its power at an appropriate time. More of that.
Conversely telling Rowling to piss off and take Cho Chang and the goblins with her is simply meeting like for like. Both valid exercises of speech.