You misread my post. Age is irrelevant, venue is irrelevant, type of music is irrelevant, your personal tastes are unimportant (so are mine - I wouldn't pay a dime to see Ed Sheeran, Tàylor Swift, or Beyonce and Jay-Z, who are the three biggest tours of 2018). A performance is a performance. If they were getting paid to play there, there is no excuse for playing impaired. Even if they weren't getting paid, there is no excuse.
FWIW, the venue owner was charging a $10 cover.
I've been playing for about 35 years, from little bars to larger theaters, originals and covers, in all genres of music. Twice people were impaired. Those were the last time I played with them.