Okay but we're not talking anger that's expressed by violent behavior or even clear significant loss of control, I'm talking people on the internet can pick up the mildest hint of anger from your tone or even subject matter. As a woman and a pretty scrawny one at that, as well as being, well, obviously very opinionated and belligerent, I have experienced every flavor of the threatening behavior you're invoking and I can assure you this has nothing to do with why people reflexively dismiss people who they think are being "emotional". More and more, the accusation of being angry specifically seems to be all people think they need to say to smugly claim to be speaking from a "rational" high ground, often despite having contributed nothing of substance to the topic at hand. Like pointing out that this person's blog post aimed at no one particular person did not really have to contend with the perception that this person was going to actually become violent at anyone, although actually I could see getting that impression from this post more than most, since it frequently explained the anger as cartoonish threats of hypothetical violence. I'm not exaggerating. When I see this in person and can make better assumptions about the genders of the people involved, this seems disproportionately likely to be leveraged against women, as are most arguments to "obvious" or "apparent" disqualifying irrationality, and this is not a shock because we are within living memory of much of work culture treating it as conventional wisdom that this should be assumed of all women by default. People really be trying to win epistemic pissing contests by posting something that looks like running "u mad" through google translate and back once, unironically, just as surely as you're trying to do that obnoxious thing of trying to invoke the gravity of situations in which people genuinely fear for their safety, hoping that gravity will somehow make it harder to question what you said for fear of seeming chauvanistically oblivious or whatever that's supposed to do
I propose the alternate theory that as in-person interaction becomes a smaller portion of most people's social experience, many have gotten worse at handling even mild interpersonal conflict without the kind of impersonal mediating forces that are omnipresent online, and this kneejerk aversion reaction can rationalize itself with the aid of this whole weird gilded age revivalist-ass cartoon notion of "rationality" that's become popular among a certain flavor of influential person of late and, especially in a certain kind of conversation with a certain kind of smug obnoxious person, seems kind of like classic Orwellian doublespeak
Also this position that "arguably almost nothing" in tech warrants anger seems super tonedeaf in a context where most of the world has become a panopticon in the name of targeting ads, you need a mobile phone owned by a duopoly to authenticate yourself to your bank, and large swaths of previously functional infrastructure is being privatized and stripmined to function as poorly as the companies that own them can get away with while the ancillary benefit of providing employees with subsistence and purpose wherever possible, while still managing to nickel and dime you for the privilege with all manner of junk fees, and offer poorly-designed phone trees in place of any meaningful documentation or customer service