If you find such a player then there is something wrong with his daily life. Such people do not find the real world challenging enough or do not find the world around them more rewarding.The exact thing that a good fun video game provides. There can be various reasons for them to think this way. They may not be happy with the way things are going with their school or college or work life, peer pressure, bad or ignored parenting. The list can be big. And so is the reason why people who don't play games think that they are bad for their children/spouse/friend.So you see, it is a psychological problem, isn't it?
The other reason I think why a game can be bad, is the game itself. 7 out of 10 games are not worth playing. They would either be gruesomely violent, have horrible gameplay or show content which is not suitable for the age of the player. This will definitely affect the person playing that game. And i think the ESRB ratings wont stop the age groups to play games not meant for them. Game developers should know that action is good, but also action should be fun. Somehow the "fun" part goes missing while creating a graphically awesome, massive action packed game, for most of the developers. And when such game falls into the hands of the wannabe player, it will only ruin his gaming spirit.