"Some day we're going to have to nuke a comet"

No.

Nuking a comet is probably the worst thing you can do to try and divert its path. At best the nuke would shatter the comet and not divert its path, meaning instead of one huge comet intersecting the earth you now have many, many huge comets intersecting the earth.

There are alternative methods out there that will nudge a comet when it is far out, avoiding the "blow it up" mentality the laymen seems to think is prevalent.

I've often wondered about that theory. If you blow the body up into small enough bits, won't they just burn up on entry? Only large pieces would make it through, causing far less impact over a somewhat larger area, so locally it might cause more damage (larger area of total destruction from impact), but globally it should cause less, no?

Bravo Newtboy !!! Yes I was thinking the same thing !!!
One huge comet blown up is NO LONGER A HUGE COMET. But lots of smaller ones that mostly would burn up on re-entry !!!!