I feel your pain. While I am concerned for and saddend by, the exploitation and use of animals the world over, it's difficult to be vegan purist. So I don't try. I do the best I can. I don't stress over a tiny amount of diary, for example, casein, in some vegan food
s. In a perfect world, it'd be easy to follow a vegan lifestyle, but, well, it isn't a perfect world...
I recall reading a book in asimov's foundation series wherein he posited that people obtained protein from manufactured yeasts. I found this facinating. He imagined a world 50,000 years from now, and probably felt that the use of animals in any form was considered to be barbaric.
Most days, I eat fully vegan, but when eating out or invited to people's homes, I will consume dairy/ eggs if they're present in food. And, if I crave icecream or milk chocolate, I do give in. For me personally, the stress involved in avoidance of dairy isn't worth it. But that's just me. I also know vegans who buy preowned wool and leather. One friend will eat dairy and eggs when he's on a road trip.