And not an ethical or philosophical discussion obviously - I mean they're talking about which animal flesh they like more, which dishes "need it", how they like to cook "it", etc.
Are you silent and just wait for the conversation to move onto something else? Do you offer a comment on the topic? Do you say something entirely different to try to change the subject? Do you do something else to distract yourself or because you're bored or annoyed/upset/disturbed by it? Do you go into another room or leave if you can?
In these moments it can be incredibly awkward, I would imagine even if you aren't an ethical vegan, maybe even vegetarians who just don't like flesh by taste preference or are grossed out by it. There's nothing to add (presuming you don't want to go against the grain of the group and accidentally start an argument and trigger everyone by making a comment expressing your own choices or views or anything).
It's kind of like if everyone is talking about their favorite hockey players when you have no knowledge or interest in hockey, except if the hockey players were also all convicted sex offenders and the conversation disturbed you immensely.
We're socially expected to be silent about our views on animal exploitation (or flesh consumption) and not even state our "preferences" or choices too loudly, but then everyone else is socially accepted to say whatever they want about the subject at any time and in any manner (including defending animal exploitation and criticizing vegans). This creates an untenable imbalance where we just have to shut up and hold our tongue when people are talking about things that make us uncomfortable or even offended.
But in those settings, but it must be awkward for them too, I imagine (unless they're trying deliberately to make the vegan uncomfortable, which does happen a lot - but most people probably don't want to, I think). It's weird for everyone. What do you do?