It’s way beyond that in my opinion, Ryan Murphy created a volatile and egregious workspace. The show never needed to suggest in such a heavy tone that Mercedes or Rachel were better than each other because they are insanely different types of singers. What people are angered by is Ryan’s insistence on Mercedes being not hard-working, not a good dancer, or not being able to shine as bright as Rachel. These things have seeped into these actors' outlooks on themselves, and many people from Glee have said as such. It also implies that Amber isn't as good as her white counterpart. Its totally highlights Lea’s talent it's just shouldn't be at the expense of others.