It's not that hard to do, but apparently it's something white people still forget about at concerts. When an artist performs a song to a crowd of white people, it's not unreasonable to expect the crowd to self-censor when necessary. If you're white, don't say the n-word. Unfortunately, as evidenced by Kendrick Lamar's recent performance at Hangout Fest in Alabama, not everyone got the memo.
As pointed out by numerous people attending Hangout Fest, Kendrick brought a white fan on stage to rap alongside him. It doesn't take that long for Delaney, the fan he brought on stage, to mess up. Performing "M.A.A.D City," she manages to censor herself the first time around, before doubling down and uttering it not just once, but multiple times.