It depends on how often you are sad. Listen everybody has a crutch or addiction....EVERYBODY. But in life you should be sober more than not sober. So if you are sad occasionally it's no big deal, but if you are sad all the time and drinking to feel better, that could be a problem.
Drinking when you're sad is a very dangerous behavior because it is the most common path to alcoholism. When you are sad you drink trying to ease the pain. It works fairly well for the first night or two, then it requires more alcohol the next time for the same amount of pain relief.
Very quickly the cycle of drinking more and more alcohol for the same level of relief reaches the point where there is almost no pain relief but lots of drinking. That is cycle of addiction most alcoholics experiences.
The person who said the experts don't know what they are talking about is completely wrong. Alcoholism is the most understood addiction there is.
Drink once or twice because you're sad, you'll be fine. Continue to do so and you're on a ride that will take you down so fast, not only hurting yourself, but all the people around, especially those who love you.
Talking about why you're sad, and working on ways to change it, works far better then swallowing your feelings with a shot of alcohol. So, what are you sad about?
If you drink when you are sad then you will never fully get over anything and then not have the skills to deal with even bigger problems when they come up. It is better to deal with what is bothering you and then get over it. Why are you so sad?