Delta Air Lines Flight Attendants Boston-LAX California

On 8/23/2014 I was flying on Delta airline from Boston to Los Angeles, and my 9-years-old son was asking the flight attendant qustions, "What movie are we going to watch tonight?" and "How long is the flight?" He was using normal voice and was polite. (During the 6 hour flight he maybe asked 3 questions total). However, the flight attand grew impatiant and started snapping at my son, rudly: "Keep your voice down, young man," and "Stop asking me when we are there, the answer would be the same." Meanwhile, she was super nice and chatted loudly for half an hour with some male passinger. I found behaviour of both flight attendents out of line, and out of professional curtesy. It felt like descrimination against children on the airplane. Do they respesent too much happiness and aliveness, freedom and esteem? BTW, we were traveling first class.