The rules clearly state:
2.2 Random Death Match - In order to kill or harm another player you require a valid role-play reason to do so. Crossfire is not an excuse for killing people nearby where you are raiding or shooting. This rule always applies unless another rule calls for an exception. During an airdrop, you are only allowed to kill people within the district of an ongoing airdrop. Police may not kill arrested criminals in the jail cells unless they are making an active attempt to escape the cells.
Causing damage for no apparent reason is considered ARDM. Stop whining, doing damage to someones armour is still considered doing damage.