The problem that older middle-class Americans had with Coney Island had to do with "the fact that young men and women were unchaperoned."
During the late 19th and early 20th centuries, Coney Island became a popular destination for working-class Americans seeking leisure and entertainment. However, as Coney Island grew in popularity, it also attracted young men and women who were unchaperoned. This was a cause of concern for older middle-class Americans who believed that young people should be supervised and that unchaperoned interactions between young men and women could lead to moral decay.
Therefore, the problem that older middle-class Americans had with Coney Island had to do with the fact that young men and women were unchaperoned, and they viewed this as a threat to traditional values and morality.