I can't offer you any advice specific to your personal situation because I don't know you, your parents, or anything about the type of relationship you have with them. However, as a parent of three grown children and one teenager I would like to offer a few things for you to think about. First, the fact that they're cigarette smokers is beside the point. Their concern about the health issues associated with smoking is most likely not hypocritical, but instead is probably based in their genuine concern for you. They're addicted to a particularly harmful form of tobacco use and don't want you to follow in their footsteps. Try to keep that in mind.
Second, try to avoid getting into a discussion with your parents (or anyone for that matter) about the relative benefits or risks associated with the various forms of tobacco use; you won't win that one. Despite what anyone may tell you, and with all due respect to others who may hold a contrary opinion, pipe smoking is not healthier than cigarette smoking...it's only less harmful in certain ways than other forms of tobacco use. Every form of tobacco use holds its own set of health risks, so don’t kid yourself. As adults we understand that, and then we make our personal choices accordingly.
Third and finally, keep in mind that you and your parents are probably going through a difficult, though necessary transition in your lives. As you enter adulthood you have to establish a healthy independence from your parents. You will not, and cannot live your life so as to please them in everything you do. You should always want to please them, but get over the fact that you may not always be able to do so if you’re going to live your own life. In turn, your parents have to learn that you’re not their little kid anymore and that they no longer hold absolute authority over all that you do. It’s a tough transition for all of you. This issue is probably less about tobacco use than it is about how to begin relating to one another as adults instead of through the adult-child relationship. Again, this is probably as tough for them as it is for you. Just go there slowly and respectfully.
BTW, if you’re 18 years old, my best to you, it’ll work out fine. If you’re 40 years old, you’ve got some real issues going on there. If you're under 18, then listen to your parents!!!