Bad primer! Baaad, bad primer!
To kill primed cases: Take the case in question, put it in a vise (base upward), then, wearing hand, ear, & eye protection, use a nail set and a hammer to give the primer a very firm rap. A gentle tap won't do it. The case can then be resized in the usual way and its useful life seems IMX to be unaffected.
The primers blow a good bit of flame out beyond the case mouth, and sometimes the primer cup and/or anvil are forcibly ejected upward. So you need to have nothing flammable right below this operation. I find heavy leather work gloves to be quite adequate for hand protection.
That's it. No big deal. I used to kill primers by chambering the cases and pulling trigger, but the above method saves cleaning, and wear & tear, on the guns, as well as working for cases that won't chamber.