For someone who drinks as seldom as I do, I find myself defending alcohol more often than not... >_<;
In my experience, any violence, cruelty, poor judgment, or other negative behaviors caused by excessive drinking are symptoms of something that was already there in the drinker's personality. Excepting the obvious physical effects, the effect of lowered inhibitions, as caused by depressants like alcohol, is that the fundamental aspects of your personality are laid bare, without guile or social subterfuge; you're simply not keen enough to be able to fool anyone, and tend to speak your heart before you have a chance to think it over, for better or worse. As someone who values blunt honesty, I appreciate alcohol for that quality.
I grew up hating the stuff with passion. My parents partied hard through most of my childhood, and drank themselves into helplessness, car accidents with my sibs and I as passenger, and terrible fights with friends and family. All through my childhood, I blamed alcohol for this, and swore up and down that I would never drink. As I grew older, I came to realize that these were sadly aspects of their personalities, which they (and not alcohol) were responsible for... and their lack of responsibility lead them to drink at inappropriate times, and in quantities that set themselves up for their problems. As with anything, self-awareness and responsibility are key. Still, there are many inappropriate times and ways to use it. Getting drunk to the point that you can no longer stand up, or that your body has to purge itself to keep you alive are obviously inappropriate usages of it. In the same sense, when your stomach is absolutely stuffed, eating an entire pizza would be an inappropriate usage of food, and your body would certainly intervene before it caused you harm.
I would say that alcohol is, by its nature, a good thing, and it has a number of positive qualities that can be enjoyed by responsible people. Many good beers have a rich, nutty, bitter taste profile similar to coffee, and though I don't care for most liquors, they tend to cover an extremely broad base of flavors, from fruity or caramel-like to acerbically bitter. The experience of being inebriated can actually tell you a good deal about your personality as well... I tend to be significantly less emotionally guarded, and anything I've done while drinking has been good-natured, and at worst a bit silly and embarrassing (ex. singing showtunes to the downtown area, and hugging my friends profusely).