While this may be normal activity on an El Al flight, the gentleman concerned was not on one, and perhaps should have been more aware of, and considerate towards, the possible perceptions of those around him.
Okay, as an innocent 17-year-old young kid he might not have been exposed to others' sensitivities, but for him this was absolutley normal behavior. Remember, we're talking about New York City here, with a huge population of Orthodox Jews. This is normal, there is absolutely nothing unusual about it.
The problem stemmed from simple ignorance (in its most basic non-defamatory term) on both sides. The kid had no idea what his normal, everyday behavior would look like to others and, apparently, this was the first time the cabin crew were exposed to it.