Because of their stans, most of them are violent, completely delusional (not to mention irrational) and obsessive. So people drag their faves to annoy/troll them and make them shut up.
Atrl doesnt hate them. Some people do though. because the only thing they care about is: sales and Gaga and Beyonce underperformed last era in their opinion
Their talent and success. ATRL treats Bey like a new artist. It's stupid since many people on ATRL go around praising Britney and have no idea that Bey has been in the industry for just as long.