Isinglass is (traditionally) from sturgeon swimbladders (is caviar a byproduct...?
) - all sorts of issues are overcome by using a clarification product - most people just say that it's not part of the beer, "just passing through..." whatever...
There was a time when a a red wine called "Bull's Blood" was just that... there are all sorts of issues for us "sad b*stard" veggies... "emulsifiers" are another fun thing... bread has "mono and diglycerides of fatty acids" to help keep it "soft", which is obtained (generally) from the stomach lining of cows, and for pity's sake, don't get me on "gelatine" and "mechanically recovered meat"...
There was a promotional item from the UK "Meat Marketing Board" saying that "Black pudding is almost vegetarian, there's virtually no meat in it..."
Here's a piece of advice... don't think about your food (or drink) if you want a peaceful life...