Leaving the superstar DJs aside, a good DJ will leave his ego at the door and entertain the people, not himself. Any DJ who comes to a gig unprepared and without a backup of chart music will learn the hard way.
OK I see where you are coming from, when the manager of the premises books you to play a certain style of music, that he thinks his crowd wants. You can be sure the crowd that was pestering your mate for chart music was also complaining to management and was not the crowd expected to be there. The owner is going to blame the DJ not himself, and its unlikely that he will be booked there again.
First time that happened to me it was also the last. I ALWAYS bring chart and a mix of certain styles, as you never know what energy or crowd is going to be in a room.
The DJ feeds of this energy, builds it up, takes it down again, plays and teases with the crowd. Its your job to let people dance.
You learn from your mistakes and this strengthens your style. Many of my best nights are when I get to play music I like, to a crowd that wants it. Then you get to be the Superstar DJ for the night. Most times though, its a job, hard work at times, but it pays the bills.