Weary Sigh...
This subject comes up periodically, so I'll try and resurrect the usual answer.
Long ago, back in the days... PPRuNe was a pilots only forum discussing pilot type stuff. Some pilots used the term SLF for passengers, especially those with a military background, as used to be the norm: Given that many of them have no interface whatsoever with passengers, beyond an en-route PA announcement, this is at least understandable - whether you approve or not is another matter.
As PPRuNe expanded and the number of forums increased, the SLF name stuck to this forum. For the record, in 33 years in the industry, 30 of which are as crew, I have never heard a single British cabin crew member refer to passengers as SLF - ever. The only exception is here on PPRuNe where it is occasionally used, sometimes by those claiming to be Cabin Crew, and often in an attempt to comply with perceived normal practise.
Many industries have phrases that are considered acceptable for use within a peer group, but not by outsiders - Medicine springs to mind. Another example might be the word that would be considered highly racially offensive if used by a white person, but is in common and routine usage amongst African-Americans when referring to each other - supposedly to indicate irony, although I have my doubts. The point I'm making is that language is powerful, and its' use requires care and compliance with the rules to avoid giving offence. Here on PPRuNe (originally a Pilots' Forum) the peer group viewed the term as being acceptable.
You may of course, if you wish, choose to take offence, or to read into the phrase something that in my experience simply doesn't exist: This forum is for passengers to offer their opinions, so you are most welcome to continue in this vein if you wish. I certainly won't prevent you, but I will go on the record at this point to say that in my view this is neither an issue, nor a symptom of an issue.
P.S.
The BA thread(s) in the CC forum have been by no small measure the most frustrating, irritating, depressing, tedious, thankless and time-consuming work that the CC Forum mods have had to deal with in some considerable time: I'm also a mod in there, along with my esteemed colleague Flaps (who for the record is an immensely skilled and experienced Cabin Crew member). The BA thread has experienced many hijack attempts, not only by extremists on all sides, but also by other parties, including passengers, all of whom have been anxious to display their various prejudices and agendas, or simply to demonstrate their own titanic cleverness and ego: While this may be fascinating for those who are in love with the sound of their own keyboards, it has usually contributed little or nothing to the debate, except to raise the global temperature and thereby promote further irrelevant posts.
I would be grateful if this forum would not be used as a receptacle for those opinions that were deleted by mods various (including myself) on the BA thread in CC.
Thanks