There are several claims that milk is bad:
The last one claims to be supported by a scientific research: http://archpedi.jamanetwork.com/article.aspx?articleid=1704826
- Depletes the calcium from your bones, causing osteoporosis
- Increases fracture risk
- Is an acidifying animal protein
- Creates excess mucus
and so on.
I'm unable to verify the claims, although I've drunk plenty of milk (1 litre per day) until I was 20 and never had a broken bone and have strong teeth. I also have a few friends that had even more milk than me and have big bones. On the contrary I don't know of anyone who drinks milk regularly and had bones problems. I know people who are intolerant to milk, but that seems to be related to the pasteurization process as they are fine with raw milk (but that's another story).
So, it milk really that bad?