Why would I want to be ethical?
Because human animals only act for 2 reasons: either to gain pleasure, or to avoid pain. Unless you're a sociopath, for most people, it would bring emotional PAIN to harm others in an extreme way. And even if you are a sociopath, the chances of the PAIN of the event outweighing the pleasure is statistically likely when you get your *bleep* carted off to jail and lose all of that "freedom" you speak of.
The greatest tyrants in history would pale beside the pursuits I would undertake.
Overconfident much? You are forgetting that certain conditions need to exist for you to even have a chance of "ruling over others", and a person who writes for $3 per month on a forum is probably in the furthest position away from power that one could be.
Are you seriously saying you would play a video game and actively elect to be the assistant to a shopkeeper? Me I would bash the shopkeepers skull in at the first opportunity in such a game and then set traps to slay my customers.
A video game is hardly a comparison to real life. Plenty of people enjoy doing exactly what you speak of, under the condition that
the situation isn't real. They aren't real people with whole lives and families that you're polishing off, they are figments of fantasy.