The newest Kim is the most obvious symbol of this regime, but the point is just as valid for every member of the royal family, the entire party cadre and all the flag rank army brass.
I am sure they all remember the fall of the Communist Bloc -- what happened to Nicolae Ceauşescu haunts their sleep.
They probably imagine hordes of starving people descending on Pyongyang. People starved and abused to the point where they just don't care anymore.
All the Army's guns might not help them then. And if the junior soldiers and officers join in...
Yep, only way to overthrow this sort of regime is by a concerted uprising and killing off the current rulers. Biggest problem is that in the ealry stages it will be a few hundred to a few thousand of the people bleeding for every one of the enemy they take out. I also wonder whether we and/or China would throw other wrenches into the mix.