Maybe because the author didn't bother to contact any Orthodox rabbis, but his claim about only wine having 'Jew-only' restrictions on it. Dairy products and bread have similar restrictions, but are less widely used.

-I've only seen Chassidic people concerned about it but chalab/cholov israel requirements mean that an observant Jew has to observe the milking of the animals. Also, most cheese produced in the US is kosher since animal rennet has become less common but try finding kosher cheese besides Cabot or President in your supermarket.

-For bread (particularly challah) some people hold by 'pas yisroel' that a Jew had to be involved in the baking, usually by lighting the oven. For challah, a bit of the dough must be taken, a blessing is said and the bit is burned. This last thing must be done by a Jew because this commandment is only incumbent upon Jews.

Since many Orthodox Jews view Christianity as 'idol worshipping' (pagan's not a very concise term) it IS an issue. You find me a bunch of Muslim winemakers....