But isn't that ingroup/outgroup-dynamic still happening? Very few westerners would consider the followers of Bagwhan 'religious', they'd rather use something like 'cultists'. Aum/Aleph is a 'cult', even though it represents itself as a syncretism between Buddhism and Christianity. Radical forms of Islam are sometimes called a cult, and sometimes a religion, depending on the speaker.
All that shift in meaning seems to do is that it determines which belief systems are considered appropriate by a speaker, and which aren't...
"Cult is a term which, as we value exactness, we can ill do without, seeing how completely religion has lost its original signification. Fitzedward Hall, "Modern English," 1873"
It strikes me as funny because the problem with the word 'religion' is noted as far back as 1873, but I'd argue 'cult' is now even less precise than 'religion'. I don't think it was always that way. References to Roman mystery religions as 'cults' generally lack the pejorative connotation.
All that shift in meaning seems to do is that it determines which belief systems are considered appropriate by a speaker, and which aren't...