Sulfite is just Campden, added at 1 Camden tablet per gallon a couple days before you pitch your yeast. The Campden/sulfite kills off the nasty wild yeasts and bacteria, and while it does hurt beer yeast and wine yeast a bit (caused them to generate more sulfur), the effects fade enough after a couple days that with a healthy pitch they're able to survive it and be the only critter in your cider.
Now, if you're dry hopping or adding other things later in the fermentation, you might want to sanitize with alcohol or more sulfite to prevent any critters from grabbing hold from that point on too.