I'll simplify this. There are several definitions of "cult". Here they are:
You're using the first and second definitions. However, most people use the third definition when referring to cults which is why most people don't consider Catholicism a cult, but they do consider the Branch Davidians a cult. For this reason, it is inaccurate to reduce the aversion of the religious to use "cult" as mere "sensitivity". On the contrary, it is their familiarity with society's use of "cult" (the third definition) that inspires them to object to people's use of the term. While their religions are "systems of religious beliefs", they may not be "regarded as unorthodox or spurious" which is what most people mean when they say the word.
I should also correct the part of my post where I said that "I won't be surprised if the dictionary definition changes soon" because the dictionary has already changed as evidenced by the fact that dictionaries including the OED and MW use the definition I'm referring to. There's also
this dictionary which lists the most popular definition first in their list.
Also, I find it funny that you laughed about my link to Wikipedia when the definition I pointed you to on the page was from the Oxford English Dictionary. That's a pretty good source for definitions, no?