I hate to be an optimist here on top of it all, but couldn't an argument be made that nuclear weaponry and related technology could be insanely useful in space exploration?
Aside from the Bruce Willis Armaggedon situations where we need to blow up big rocks coming towards us (or nudge them a bit with a gigaton bomb around Jupiter), I think nuclear weaponry and explosives could be useful for:
1. Lunar or Martian mining or interior terraforming. Build caves in the moon.
2. Clearing the asteroid belt if necessary.
3. Altering the orbit of natural satellites of other planets. Create or decrease tidal forces.
4. Atmospheric detonation of a nuke could be useful for clearing a supervolcanic eruption's soot from the sky here on Earth.
5. Killing aliens that are hostile, whether they look like WWF wrestlers with crab faces, giant insects, big elephants or Area 51 critters. Morality may not be a concept understood by another spacefaring species, or global extinction of life on another planet may seem like a very good idea to us. I don't think PETA would complain if we finished Sigourney Weaver's job and nuked all the bugs from orbit just to make sure.
1. No, there are a lot easier ways of mining than by nuking stuff.
2. The belt isnt that dense, all of our probes that have traversed it made it through without being hit, the current odds of being hit while traversing it is one in a billion.
3. Unlikely, the force released by a nuke isnt that great. Bear in mind that when SL-9 hit Jupiter,
one of the fragments (admittedly the biggest one) caused a bang in the order of 6,000,000 megatons of TNT.
4. That would probably cause more harm than good.
5. Aliens on their planet are not the aliens in that situation. Besides, even if we did get there I would hope we would have better stuff than nukes by that point.