Not uncommon among real people when they enter a new world. Take for instance, bison being nearly eradicated within a century of significant settlement west of the Appalachians.
Not to mention, new players were probably practicing combat. It's not like anyone would normally have concern for killing virtual goats and rabbits.
I have friends with hunting ranches where I could go shoot anything I want, like Axis deer, Ostriches, etc. I don't hunt. When I played UO I killed thousands of rabbits to get pelts to raise my tailoring skill. I don't see how these correlate whatsoever. I've also mowed down people in Grand Theft Auto but am very cautious around pedestrians in real life.
Humans have hunted for nearly the entirety of their existence. Mammals' forms of play simulate predation and evasion. Whether or not it's a good thing is subjective, but that humans innately find some forms of violence entertaining is pretty clear.
I'd like to add, there's a current advert for an Xbox game, the backing track is the Beach Boys "Wouldn't it Be Nice." In any case shooting galore...as a Xmas gift? We're on the cusp of legit virtual reality and our goto is still kill kill kill?
I'm not sure why relegating destructive tendencies to virtual worlds is a bad thing. There is plenty of evidence to suggest that humans have innate proclivity to violence. The percentage of men who die violently (as in, at the hands of other humans) is around 25%. This is compared to ~2% in the 20th century, and even less today. Many mammals' forms of play function as preparation for violence (either capturing play, or evading from it). There's strong reason to suggest that humans innately find violence entertaining and compelling - at least some forms of violence.
The fact that we've managed to relegate this behavior to the virtual world, rather than the real one, seems to be a good thing to me.
I was actually part of the player population at the time. My friends and I would wait for mountain goats to spawn so that we could kill them and take their hides -- goat hide was the easiest way to acquire leather to make armor and sell for an outsize amount of cash for the effort and skill. I think it also improved a couple important stats. We were not the only players employing this strategy.
So from what I recollect as a player the killing was economically motivated rather than motivated by ultraviolence. Not sure if that's any better...
I think that’s an overly serious interpretation that also doesn’t account for a different game mechanics.
For instance, take a very early RPG, Miracle Warriors. We played this for weeks before we understood that you weren’t supposed to kill certain creatures, and that it lowered your reputation score. Even after we understood that, it’s not like we were really trying to role-play ethically – we were just trying to gather experience and money. Or what if your character is evil? It’s just a character. Eventually, there were parts of the game that you couldn’t access unless you had a high positive reputation.
Not to mention, new players were probably practicing combat. It's not like anyone would normally have concern for killing virtual goats and rabbits.