Well veganism is about reducing suffering. Like if the cows didnt suffer to produce that milk. Like no forced insemination, calfs aren’t separated from their mother, male calf’s aren’t slaughtered, the cows don’t have unnaturally large udders, you only take the over production and not steal the food from the calf and the cows live a good life then you could argue that the milk is vegan. But milk is not produced like that so milk is not vegan.