You can call me anything you want. Just don't get me to my destination too late!!!!!
With ash delays, the word "patient" came to mind.
And, with low-cost the fashion, I thought of "shoppers."
Enough of that.
I don't find the term SLF objectionable and indeed find it rather humorous. As we have seen in these comments, the industry does not seek to offend passengers. It has a sense of humor.
More importantly, it is part of the culture of the airline industry. I think one respects other cultures. Part of respecting other cultures is to partake in aspects of other cultures that you normally would not, such as language. It is one way of making connections. No pun intended.