NASA's vaunted "Asteroid Redirect Mission" is now widely regarded as crap. It doesn't give us any new knowledge, it's not a good intermediate step for human colonization of space, and it's been mismanaged so badly that you could tell me it had been infiltrated by Russians intent on destroying America, and I wouldn't much doubt it.
But it does have one saving grace: it's our best shot if we ever find an asteroid headed for Earth impact.
I found this out sort of by accident - I was playing Kerbal Space Program, which has a NASA-sponsored module for doing asteroid redirects. I had a ship designed for that in orbit, and was looking for a good target.
I found one. On a direct intercept course. About a week out.
To make things worse, it was at like 80 degrees inclination. To cut a very long story short, I managed to redirect it to aerobrake, then stabilized the orbit so it wouldn't eventually deorbit.
Now, I fully realize that was a game, and that rocket science is actually a lot more complex than strapping a shitload of boosters to everything (my standard design). But the basic principle remains - something that can redirect an asteroid to enter lunar orbit is also something that can redirect an asteroid off of an impact course.
I don't know if that fully justifies the program - it's an absurd expense for what we get. On the other hand, what price can we put on avoiding extinction?