Maybe one star isn't a polite rating, but in many countries, you rate honestly a business , not with intent "not to hurt its feelings"..
Black bull's prices are average, so i can't give a star right? It's definitely not cheap. Black bull's atmosphere is regular, so why give a star ? ok. The service is what kills it. I don't mean the kitchen service because the food usually comes very fast so kitchen service is definitely deserving of a star for their hard work.
The worst part of the service is from front of house. Maybe it's not all their fault. Because the owner/management can stress as much as they want on hiring people who are happy or smiling, but you need to understand that people only smile when they get paid properly. A friend of mine has been waitressing in Canada/Toronto for years now and says it's insane how poorly paid servers are, especially when their tips even get taxed... So my bad experience today at Black Bull, with the Asian waitress who did not even say thank you after i made a big purchase and simply put down a receipt in front of me then left - Well maybe she isn't treated well herself.