If you blow it up before it comes down, congratulations, you've just made a shitload of space debris.
If you try to blow it up on the way down, tough titties, you're out of radio contact.
A timer might work, I suppose, halfway through re-entry. But at those speeds, the sharp change in angle caused by an explosion could increase the possible impact area many hundreds of times.
Besides, anything that comes into the atmosphere without heat shielding will not exactly be intact by the time it hits the ground. Not satellites, broken shuttles, European supply pods, whales or potted plants. You'd have to be bloody unlucky to get hit.