and not using loaded lines like 'fake-ass rapper how you think you got juice?'(c)KRS but a line that indicates they're actually using the term 'rapper' as a form of insult.

The only times I can think of it is when used by a rapper who is trying to pretend he's a pimp, drug dealer or crime boss instead like 'I am not you, rapper' on Clipse first album type of shit (which of course, is silly for an entirely different set of reasons).