Everyone is guilty of masking who they are and what they want at some time or another. For example, when we want something from our parents we usually don't demand it, and sometimes we do nice things without being asked (with a hidden motive) in order to get what we want. Another example might be people involved in scams that take advantage of people and sometimes even ruin lives.
Zaroff and his men are no different than everyone else when it comes to masking their motives and putting on heirs by having good manners and living an ultra civilized life. They want their "visitors" to buy into their game, while the majority of society is not as brutal, they certainly do the same thing.