Many people suffer an allergic reaction to certain sulfites, including those that are commonly added to wine as preservatives. However, since there are several wine makers who add sulfites to none of the wines they produce, people who would like to drink wine but are allergic to sulfites can drink wines produced by these wine makers without risking an allergic reaction to sulfites.
The assumption on which the argument depends is that sulfites are not naturally present in the wines produced by these wine makers in amounts large enough to produce an allergic reaction in someone who drinks these wines.