Milk gets a lot of bad press for a variety of reasons. Some people object to farming methods - cows have to be kept pregnant to produce milk and where do all the baby cows go? Normally the dinner table - you can understand why veggies and animal rights lobbyists object to the dairy industry.
Others bemoan its fat content, the presence of various additives and hormones...
Whatever. I'd suggest that as with anything else, milk - preferably skimmed or semi-skimmed - in moderation is fine. Unless you have an allergy or a lactose sensitivity.
If you're lactose intolerant - lactose is the sugar in milk - your body doesn't produce enough lactase, the enzyme that digests lactose. The result is bloating, flatulence, diarrhoea...all very unpleasant!
Either drink lactose free milk or an alternative like soya milk...which also has its critics! I personally drink a lot of soya milk as I'm lactose sensitive - more than a few cups of tea with milk and I'm in trouble!
Let's face it, there's a new food/health scare practically every day. Believe them all and you'd eat nothing at all!
Milk is packed with protein, vitamins, minerals, calcium, etc and is a valuable addition to your diet. A few glasses a day or with your breakfast cereal is unlikely to do you any harm.
If you like it, then drink it!
Cheers,
Marcus