That's not your son being entitled, that's him being entertained in a sandbox. Even without video games your kid will stand up action figures and kill some of them with the others. Even without action figures at some point he'll play a game where killing is part of the play. Even animals in the animal kingdom do mock battles with their fellow lion cubs and wolf pups. It's completely natural.
If your son thought he was "entitled" to that place it would be a form of entitlement.
Most children start out feeling entitled. Learning that the world doesn't exist for their benefit is something that is learned. Even games teach you the concept. The game doesn't care about your goals and won't modify it's rules just so you can reach those goals. You learn while playing the game that there is a system there you need to work within. You can learn to exploit that system to reach your goals but the system itself won't modify itself to meet your goals. Games don't teach entitlement they teach you how to understand and adapt to a specific system to reach your goals.
