I have worked in mental hospitals, retails sales (my father's store), as a teacher, and in several businesses of my own. I have had plenty of gwumpy customers. Many down right obnoxious ones and more than a couple of violent ones. In fact, sometimes it has been the ones for whom I have done the most who have turned out to be the biggest jerks.

So it goes.

I have sympathy for people who work in service. As I said, I try to treat them as I would like to be treated and even to brighten their day a bit with a smile and understanding of what it is to do their job. I wait my turn, I get out of the way of anyone who is working while I am not ... in restaurants, in planes.

However, that said, there is no reason to assume a special set of circumstances any more for the FA than for this guy or for any passenger.

I have seen confused and elderly people - some who have obviously not flown much - treated like dirt because they don't understand the culture of the airplane. I have seen people who don't speak English treated like dirt - even on international runs to and from countries of their mother tongue - treated like fools and naughty children because they don't understand quickly enough to suit Ticket agents, gate agents or FAs.

Maybe the passenger in the OP had had a terrible day. Maybe he was rushing home to a sick person, a child birthday, a well deserved rest. Maybe he didn't hear the FA. We don't know that and cannot assume otherwise.

The FA is paid - however little - to be the professional. This puts the major part of the responsibility to see that interaction with customers turn out as well as possible and leaves them with no excuse to take out frustrations from prior encounters out on a new customer.

I still don't understand why, given the info we have from the OP, some feel the need to invent reasons for the FA to have acted like the SS.

Best wishes.