I am trying teach my teenage son that it is wrong to be attracted to slim girls. What can I do?

It has NOTHING to do with you whether your son likes slim women or not, and furthermore i think it is disgusting that you think only "heavier women" should be allowed to look attractive. How would YOU feel if you were naturally very slim, and you had tried everything possible to gain weight, and you felt terrible about it because you think being very skinny is unattractive and you log on to a website and see a horrible woman making you feel ( if possible) WORSE than you did before? Because that's exactly what you just did to me.