I've heard many people say being a vegan is unhealthy. As a general rule I find this to be an odd phenomenon. Generally when you dig into this person's statement about veganism being unhealthy, it usually ends up being due to one of two things. Either they have are completely misinformed about nutrition and veganism in general, or they have a friend/family member/acquaintance who is a vegan and is unhealthy. They then proceed to base their entire outlook of this lifestyle on this unhealthy individual.
There are some seriously unhealthy vegans out there. Being a vegan does not directly equate to being healthy, just as being an omnivore does not equate to being healthy. The human diet is far more complicated than that. If you are going to "go vegan" for health reasons, just cutting out the animal products is not going to make it so!
Look, I've met the unhealthy vegans too. The ones who live on white refined bread, candy, white rice, semolina pasta, french fries and processed soy products. Refuse to eat any kind of vegetables because they don't like the taste. You know what? If you added meat to that diet it would still be unhealthy!
The bottom line is this, just being a vegan does not make one healthy. It helps as usually it does force you to eat more vegetables. However if you do not cut down on processed foods and continue to eat like crap then not eating animal products is not going to help. So next time you meet someone who has a friend/acquaintance/coworker/family member who is a vegan and is unhealthy, ask a little bit more about their dietary habits. Perhaps you can educate them a little more about the importance of a balanced diet, even as a vegan.