Yeah, that question needs a little clearing up.
If my RDA attacks your face-up defense postion "Krebons", you can activate "Krebons" effect to negate the attack. If you do not, the attack goes through, "Krebons" is "destroyed by battle", but then RDA's effect kicks in and destroys it again (I know, go figure) with its effect and sends it to the graveyard immediately. Even if I attack something else with my RDA, like "Giant Rat" and you don't stop the attack with "Krebons" "Giant Rat" gets "destroyed by battle", but then RDA's effect kicks in and destroys both "Krebons" and "Giant Rat" with its effect (too late now to activate "Krebons") and immediately sends them to the Graveyard, and, although "Giant Rat" was first destroyed by Battle it doesn't get its effect. Lest anyone should think that it is just because it was prematurely sent by RDA, it is the same for cards like "Apprentice Magician" that only need to be destroyed by battle.
I know that was a bit shotgun, but....