My observation is if:
I had a mundane job as theirs, my attitude will generally be reflective of the people I deal with. If I get a smile I would most likely smile back. If I get an attitude I would most likely give some as well for my own psychological well being (nobody wants to be a door matt).
If I searched a thousand people a day, I still don't think I would get my jollies from my job. That would not be where I would look for that kind of fulfillment
If I had to deal with people who just refuse to understand and appreciate the rules that have been applied just so they can argue with me (a lowly security guy) and hold up the rest of the line. I would not have a good attitude towards my job so excuse me for not being partuclarly pleasant.
Now that the lines are getting longer because of people who do not want to cooperate. I look back and see endless lines of people who are now getting frustrated because of the longer than necessary lines. The longer the lines get the more annoyed and unpleasant the people I am dealing with are getting. - It is snowballing.
Then I realize that the next person I pat down might simply want to bomb the Security checkpoint I was manning and not the planes or terminals I was trying to secure. Oh no. This job is beginning to look risky as well.
This job is really beginning to suck.
I think I will go see if their is an opening at the Burger King near my house.