Jan van Leyden
Adventurer
Actually, you can actively hurt your opponents if you want- if you realize that they need, say, two cows to finish their cattle breeding program, you can buy the two cows before they can and make tons of hamburger. Then you eat delicious hamburger while they shriek in rage.
Right, but not "hurting" in the sense of killing their family members, torching their fields or slaughtering their animals, i.e. actively taking something away from them.
The only thing you can take away is their chance do to something by blocking that action. This can really hurt because of the long sequence of actions you have to perform to achieve something, but this usually happens because the active player needs this action too, not because he wants to hurt someone.