Menzies wants the lounge to cater to customers in ways that make it money. If getting the lounge certified for some halal-labeled products that help it make money and provide me with a superior lounge experience at CPH then that is no more skin off my back than if they get the lounge certified as providing some eco/organic-labeled products.
The airport and lounge operators are private companies, so they will do what they think makes them money. That includes considerations for how they source and provide food and beverages, what products and services they want and how they market themselves. Concerned about passengers wasting water, so boycott the lounge over its providing shower facilities? Give me a break. It's as meaningful as boycotting the lounge because it will provides alcohol at no additional cost to the lounge guests. If an alcoholic doesn't want to consume alcohol, don't consume it. If someone doesn't want to consume some kind of meat, don't consume it. If it costs the lounge operator money, then perhaps even the boycott dreamers will get their way.