I have been intrigued by space flight for a long time, so I love these kinds of conversations.
While not about stopping asteroids, I find it very exciting that NASA is currently examining the possibility of sending humans to an asteroid. To me it seems like the logical step before sending humans to Mars. Many explorable asteroids are much closer than Mars, and the unique technological and engineering challenges encountered on an asteroid mission would certainly add to the knowledge necessary for a much longer trip to Mars. NASA would have to use knowledge from Apollo, Skylab, and the Shuttle. The experience gained from landing on the Moon would be utilized, the "Wet Workshop" concept would come from knowledge from Skylab, and the experiences of living for long periods in space comes from the Shuttle era. There are so many exciting possibilities for humans in space, not only if NASA succeeds in getting the Space Launch System operational, but also if the market can develop innovative systems to complement NASA technology. Ultimately, these technologies could not only be utilized to send humans further and further into space, but could also be used to potentially protect Earth from threats in space.