Demographics. It may not be the case anymore but in the early days of the internet it was a majority American males. That trope has stuck around.

And statistically, vegans are roughly twice as likely to be women.

It's not just the Internet. I'm vegetarian and my wife isn't, but servers often assume the veg meal is hers when the food is up

Because even now 2/3rds of vegans are women?

And the number used to be MUCH HIGHER.

So it's natural assumption to make.

That's easy. Real men only eat meat. If you don't, your either a female or a soyboy. That's why my diet is 80% meat and 20% cheese - my anal cavity may be more plugged up than a bear mid-hibernation, and I may die of a coronary before I'm 40 years old, but at least I can say I died a fucking man. An alpha male if you will. Now excuse me, I've got a 2lb steak and half a Gouda wheel to to eat so that I can take my 3 hour shit before going to bed. No body said that being a real manly man was easy.

I'd never encountered this (though I'm not a vegan) but it does seem like that the majority of vegans are women, so I can kind of see it:

https://veganfta.com/2023/02/17/is-veganism-led-by-women/#:~:text=A%20YouGov%20study%20of%202021,men%20and%2061%25%20as%20women.

I assume everyone on the Internet is a dog.

Long ago I remember an argument in favor of rule #30 "There are no girls on the internet" which I will paraphrase:

The internet gives anonymity and if you have something of value to say, it should be able to stand on its own regardless of one's weight, sex, religion, preferences, location or such. If you have to chime in that you are a girl, then you are either FBI (see rule 29) or looking for attention, but with nothing valuable to add. If you have nothing to add, then we go to rule 31 (show pics of your tits or get out).

Now, the reality is that such sentiment is sexist and ugly, but there is a general truth to the concept of an idea standing on its own merits regardless of source. Current social pressures lead to the behavior in question in that we've been somewhat conditioned to think that a) computers are for boys (this has become far less of a stereotype since smartphones became a thing), and b) veganism is unmanly/stupid (I don't understand why this still has traction, either, given Arnold Schwarzenegger, Carl Lewis, and a bunch of butch people are vegan).

rules of the internet (some NSFW)

Nobody here old enough to remember rules 30&31 of the Internet lol?

For the first systement, yes, there are a lot of women on the Internet nowadays. But there also are a lot of men pretending to be women, and a lot of creepy men, so I'm guessing a lot of women just don't mention it or pretend not to be one just to get some peace.

It all boils down to stereotypes, IMHO. Every time you're making such statements as "all X are Y" when talking about groups of people based on one criterion, you're stereotyping. Such broad generalizations are rarely useful outside humoristic tropes, and even then...

My guess would be that with the huge amount of American males (it is a big country after all) people just assume. And women are known to care about animals more, whether that is true or not.

I've been called a guy before and my name doesn't exactly strike people as male. I am female. I've been on the internet long enough not to care.

I'd guess the America part is that English is a kind of standard language for the most popular sites, so you'll find a lot of non-native speakers using it across the web. However, from the reader's perspective, all you know is they're speaking English, and the country with the most English speakers in the world is the USA, so it seems like there's a good chance you're American.

As for male, I'd guess it goes with the association of males being on computers more than females. At least for forums like Reddit.

I think for vegans, it's the association of women shooting for slender bodies while men shoot for bulking up. If you want to bulk up, meat is a great way to do it. Veganism is a great way to lose weight.

I don't, but the only vegan I know is a male, so I imagine him when I hear or read the word vegan. He's a pretty cool cat.

It's because when you take small sample size of "people on the internet" you'll get either completely random set of beliefs and assumptions, or you'll get beliefs and assumptions that you're prejudiced to project onto the wider sample.

Men aged 25-45 account for something like half of all beef eaten in America. So if you’re not gonna eat meat you’re more likely to be a woman.

Easiest stereotypes to confirm? most likely that.

I do not assume.

Only if you behave like loud, ignorant and insufferable... :-)

The second epithet is rather boring, I say that as a vegan, compared to the first one: To be imagined as US-born, white, middle-class, able-bodied, suburban, slightly anxious, heterosexual, cis-male person working in an office to sustain car, house, consumer goods and vacations is just not enough to represent the fediverse's, the internet's capabilities.