A lot of vegetarian things taste completely different to meaty things, and are quite nice in their own right. So just because someone isn't adverse to eating meat doesn't mean they don't also enjoy vegetarian dishes.
But if there is clearly a limited amount of food available to people who are more restricted, then I wouldn't take any. I was at a dinner party recently where we ordered several dishes from a Thai place. Two happened to be vegetarian--one of them is a personal favourite of mine. It isn't a vegetarian version of a meat thing, but just a particularly delicious dish that happens to not have any meat in it. Even so, I asked the two vegetarians present if they'd mind if I had some, because I didn't know how hungry they were and if me taking any would mean they went home hungry.
Regardless of how good it tastes or what you prefer to eat, if you have other options available, then you shouldn't take food prepared for a specific group if it will mean that they won't get enough. Wanting to try it is all very good and well, but not if it means other people go hungry. That's not polite at all.
It's clear, OP, that the people at the gathering you described didn't think about the fact that they were preventing others from having enough food, so they must have needed clear instructions. It's good to prepare more than enough, but sometimes that just doesn't happen. In that kind of situation, maybe, after putting down the veggie sausages (or whatever), I'd just go straight out and say, "Here are the veggie sausages! If meat is an option for you, then please don't take these until you're sure the vegetarians among us have had their fill first. I'd hate to see anyone go hungry!" Or, depending on how the food was being served, I'd offer the dish specifically to each vegetarian in turn before putting it where others can help themselves.