First off, most impactors are not that large.

Two, a large number of the are comets or comet fragments, not asteroids.
Rates of travel and reflectivity of the two vary greatly.

Three, it is only necessary to divert an impactor's course by say two Earth diameters.

While smaller objects can be handled non nuclearly if detected EARLY,
what may be necessary to do this is stand off nuclear charges.
The key to non-nuclear options is EARLY detection.

A small change in direction out there means a large position shift here near the Earth.

The "futility arguments" have often been promoted by both manned Mars enthusiasts
and those legitimately concerned with the technologies of nuclear explosives.
While the second group is admirable, the impact hazard is not exactly
theoretical.

Four, the sooner Weiler and Morrison are relieved, the sooner we'll have
a handle on dealing with the impact hazard.

Five, General Worden knows the impact hazard, and its politics, and is a candidate for NASA Administrator.

Six, I've had a stroke and am typing this using one finger on my left hand.
If my work helped manage to save some lives...

E.P. Grondine
Man and Impact in the Americas