I grew up with an alcoholic father and a mother who believed it was the sum of all evil. Although I could see what it did to my father and his marriage I always felt like I was different, and in the beginning I was. I started drinking when I left home at 19 and it took a few years for it to get to the point of interfering with my life.
Now, at 24, I've decided that the problems it causes in my life just aren't worth it. I don't think the "alcohol is evil" attitude solves anything. I was a good kid, but just had to find out for myself. It's hard to believe that alcohol is evil when you hit college age and everyone you know is drinking all the time.
I think it would be more beneficial for them to hear about your experience. I was told at one point that my grandfather (on the alcoholic side) used to drink heavily in the early days of their marriage, but then gave it up completely at some point. I've never seen him with a drink in his hand as long as I've known him. I really believe he came to the same conclusion I did about alcohol. I've gained more strength from thinking about his example than from all the "alcohol is evil" lectures I heard as a teen.