The term 'Self Loading Freight' is positively respectful compared to many industries terms for their customers/passengers/etc...
The ambulance service has some pretty horrendous ones eg: FUBAR BUNDY. F***ed Up Beyond All Recognition But Unfortunately not Dead Yet.
I've heard a chef routinely refer to his diners/customers etc... as 'Pirahnas'
A gym instructor who calls her customers/instructees her 'slaves'
Every so often, some bright spark MBA, some distance removed from actually dealing with the public comes up with a brand new name for their customers, optimistically thinking it won't get corrupted into some term of abuse. This artificial language control is gerally short lived.
The Police in a certain Antipodean Isle were encouraged to call people they dealt with 'clients'. Didn't work for some reason.