No penance for eating honey. It's not a sin. However, lacto-vegetarianism for Hindus, Jains and Buddhists is a slippery slope ultimately condoning himsā unless one lives on a dairy farm, or obtains milk from one. Even then, unless the cow past her prime and ability to produce milk is then kept as a family member or pet and allowed to live out her life naturally (we can't forget the bulls too), she's most likely shipped off to a slaughterhouse for pet food, leather and gelatin. I'm sorry to say it, but even in temple when performing abhishekam with commercial milk, yogurt and ghee made from commercial butter is contributing to the demise of gomata.
The answer, imo, is that we do the best we can in adhering to ahimsā. Especially being mindful and perhaps saying a prayer of thanks for the sacrifice gomata is making when she is raised for dairy production. The California cheese tv adverts talking about happy cows are somewhat misleading because they don't describe that those cows may become very unhappy when they stop producing milk. Of course, most people wouldn't care anyway.
What were we talking about?
Namaste and thank you, it is really shocking and sad to think about gomata being betrayed by cruel masters once she cannot give anymore milk. I can remember as a child the reaction and sad hurt feeling of other neighborhood children, no matter background or religion, asking WHY? WHY? if they happen to hear of such things. Om Namah Sivaya]