Alderaan deserved it

[Sir Slash]

And if you're Imperial, it's considered "un-manly" to look out the window to see where your enemy just went to.

[Nefaro]

For a Death Star full of Imperial Stormtroopers, I'm surprised they actually didn't miss the planet ... just sayin'.  8)

Yes, it's totally out of character, isn't it?

Even Imperials can hit the broad side of a planet. 

There's a threshold somewhere.  Planet-sized objects are on the "can hit" side.