I eat dried fruit each day. What do the sulfites do inside a person's body, and why do some people say sulfites are bad?

Ignorance, mostly... Sulfites are added to dried fruits to keep them from turning brown; they occur naturally in some things, e.g. Wine & beer. Contrary to popular perception, sulfiting agents are not teratogenic, mutagenic, or carcinogenic - but you can be allergic to them. The fda puts them in the category of "generally regarded as safe." so if you're not allergic to them, eat your dried fruit and don't worry.