A quote like "You cannot justify human slavery, or torture, or murder, so how can you justify doing the same to elephants?" could be seen to imply that in the poster's eyes, elephant lives have the same value as human lives.
If animal lives are of equal worth to human ones, then eating them for food is wrong too. After all, you can't kill a human and say it's okay because you ate them afterward.
Elephants may be intelligent and empathetic but are they really more so than pigs, cows, and other common meat animals, to such a degree that their lives are worth so much more? There's a lot of stuff coming out now about various animals indicating they're intelligent, have emotions, etc. If a wild pig killed a legal hunter and we had a thread about it in NeoGAF, would we have the same posts saying the hunter deserved to die?
Anyway, some of the posters in here might actually be vegetarians or vegans, and some
might have an ethical framework that allows
them to differentiate killing an elephant from killing a pig to such a degree that they can justify their posts. Maybe that's true of all the posters, but it's definitely an interesting question to ask.