Personally, I will strongly try to be vegetarian, but eat meat
rather than starve (a situation that arises when travelling).
if a venue is chosen that forces you (or me or others) into
a "meat or starve" or, much worse, "eat something severely
damaging to health or beliefs or starve" situation, is that
really an acceptable venue?
Yes, it is.
If a venue is inconvenient or uncomfortable for a small percentage of "regular"
IETF participants, that does not make it a poor choice of venue.
We might as well go back to the debate about location: only a venue that is a
convenient 10 minutes from my home is really a suitable venue.
I venture that "starve" is never a real outcome, but "go to a supermarket" or
"bring food in your luggage" are alternatives that need some planning and are a
small inconvenience.
Adrian