No, fuck that. A host isn't a servant, fine. But if they knew the person and still made only food, they had to pick shit out, they are just bad hosts.

You're very much presenting a doomed if you do, doomed if you don't scenario. As a picky eater (non vegan) I've found that if you're unwilling to eat something a host made they get upset. They may never directly say it, but there's always some negativity. Bringing your own food is considered disrespectful, for better or worse. The "rules" of politeness and manners in these types of situations sadly don't follow much logic.

So, if a host knows there is a vegan and prepares a dish with meat in it, what can the vegan do? Separating it out doesn't seem good, there's still probably meat juices and things they don't want mixed in. Bringing their own food will seem rude and disrespectful to many hosts. Refusing to eat will likely be viewed as them being overdramatic by the hosts.

So while it's true that the host has no true obligation to prepare something separate, they're still knowingly putting the vegan guest into a catch 22 scenario. The host isn't under obligation to provide food at all but they are and they're knowingly choosing something that a guest can't pick due to dietary restrictions.

I'm basing this on the types of gatherings and families I grew up around in the American southeast. It's not universal, of course. Even here it isn't. But I also believe the types of hosts who would be tolerant of you not eating or bringing your own food are also the ones who would be polite enough to separate the meat before and cook them separately or they'd make something the vegan guest can eat just in general.

Nah, it's not hard to make dishes modular. Not doing that is entirely disrespectful.

But if the hosts show no interest in making dishes vegan-possible, I usually bring my own food anyways.

If there's no coordination up front, the burden of which must fall no the hosts, I don't see any issue with the vegans in question taking care of themselves while the omnis take care of themselves. Visiting each other can be more than sharing the same or a similar meal.

It's kind of the same thing when hosts ask guests to Bring Your Own Beer (BYOB). With that, the hosts make the request explicit. With vegan food, it's more implicit unless the hosts tell the vegans to do so.