As I understand it, you're saying that people are advocating for the free expression of ideas - and yet, when people use that freedom to insult them call for their termination, they get mad. This seems contradictory and unfair to you. If I want the right to say whatever I want, then I have to accept that some people will choose to use that right to say things like "enoch_r is a despicable human being and his employer, family, and friends should all know about it immediately." Is that an accurate summary of your views?
In response, I am saying that norms like we have on HN (such as the principle of charity) contribute to the free expression of ideas. If we didn't have those norms, people wouldn't feel free to investigate controversial ideas, or have discussions like this one, and the intellectual climate would be impoverished.
Similar norms contribute to the free exchange of ideas in academia.
The letter advocates for such norms to be defended in academia.