If I was vegan and found out after the fact that a meal that I enjoyed contained animal products in it that doesn't mean I'm some hypocrite for consuming it at the time. Whether I enjoyed it or not at the time it still breaches some ethical standard I have, abstaining from it from then on would be the expected outcome.

The same works the other way, and actually a lot better IMO.

Let's imagine a scenario with two identical restaurants with the exact same quality of food.

One sells their dish as a fully vegan option, but doesn't tell the customers.

Hardline "oorah, meat only for me" dude walks in and eats the dish, loves it.

If he goes to the other restaurant and is told beforehand that "sir, this dish is fully vegan" - do you think they'd enjoy it as much?

Prejudices steer people's opinions, a lot. Just like people stop enjoying movies and games due to some weird online witch-hunt that might later on turn out to be either a complete willful misunderstanding of the whole premise (Ghost in the Shell) or a targeted hate campaign (Marvels and many many other movies starring a prominent feminist woman).