I see it like this. Yes, it's a battle and what's said is apart of the battle, and sometimes after the battle everyone knows that there are no hard feelings about what was said. But to me, personally, something like that, speaking on someone's dead mother and/or father, is a little fuck up. I personally wouldn't go that far in a battle based on pure respect, whether that would have cost me the battle or not, and I think that's where Al was coming from.
But on the other hand, F.A.B. still did kill him.