As long as North Korea doesn't get their hands on them.
You've convinced me in your earlier opinions question
They have very little impact on an asteroid. There are many other ways http://news.discovery.com/space/asteroids-meteors-meteorites/top-10-asteroid-deflection-130130.htm. Sure Nuclear weapons might add something, but we could always re-build a few even if we don't have any lying around.
Would you rather have one big asteroid hit us or a whole bunch of smaller ones raining down everywhere? I wouldn't rely on nuclear weapons to blow up an asteroid into small enough peaces so that they could burn up in the atmosphere. There are much more better ways to go about this.
What if they blow up in transit? Then what?
A nuclear explosion in space near Earth could increase potentially harmful radiation levels. Also, instead of one big asteroid, you'll have hundreds of smaller ones careening towards the planet. Multiple asteroids are harder to target than just one. Also, don't forget how expensive the nukes and the property damage would be.
I like my asteroids not being radioactive.