I have deprimed live primers many times. The technique is to do it in a single stage press and use a slow downward press on the press' handle with NO impact, jarring or quick motions. Primers don't go off on compression pressure, just sharp impact. I have never had even one go off. Even if it did the small explosion is totally contained. No harm, no foul. Don't reuse these primers as the de-priming will compress the anvil to the point there will many failures to ignite. Put them in a jar and cover them with WD-40 for several days and then dispose of them. I never did that while they were still in the brass because whatever one uses to kill them still has to be removed from the interior of the brass.
You might think about tumbling the cases with the live primers still in and then de-priming as described. I can assure you that dry tumbling cases with live primers WILL put tumbling media into the primer hole. It might go off but the standard deviation will go sky high making for very inaccurate ammo. Wet tumbling will kill some of the primers, but not all of them as one would expect.
