I think it's a great question.
A lot of what I see on this site isn't Monster Fish Keeping....it's Monster Fish Cruelty. Keeping ultra aggressive species in such heavily stocked tanks that the fishes nature is somehow changed, keeping fish so large that they can't comfortably turn around in their tank, exposing them to poor quality water because of the constant battle to keep nitrates down in tanks with such a heavy bio-load...I think that is cruelty.
On the flip side, recreating their natural habitat as best as possible, giving them plenty of room to swim, clean water to live in, a healthy diet, as opposed to the brutal realities of nature (competition for food and the constant threat of becoming prey)...well, I think my fish have it pretty good.
A lot of the guys guilty of poor husbandry on this site (I can name names, but I won't) use the argument that keeping them in a "glass box" is selfish in and of itself so anyone arguing that a fish needs more room is a hypocrite. So by this argument, we are all guilty and it's only a question of how relatively guilty we are. It's interesting that the guys that use this "an aquairum is unnatural to begin with" argument to rationalize their decision to buy enormous growing fish without the resources to care for them are the ones that typically have entire threads dedicated to fish they have killed. Some of these true montsters live for many decades, and these guys think they are cool because they were able to keep them alive for a year or two before they croak? To me, that's not a success.
Let's play a game where we change the creature to something people care for, say dogs. What if someone had a thread with pictures of 15 dead Golden Retrievers because of the owners failure to properly care for the dogs...would we still shrug it off and think no big deal?
What if we posted pictures of a pit bull with it's head ripped off by another pit bull? Would we think that was cool, or acceptable?
Yet when these guys do it with their fish, some of us offer our condolences to the OWNERS of these poor fish? Are you kidding me? They killed these fish and we feel bad for the moronic owners? That's just plain stupid.
Rant over.