Well, first and foremost, I'd stand by the idea that the Lutheran family has no right to impose on the store owner if the store owner doesn't want to sell to them. We made it thousands and thousands of years without having grocery stores, I see no way to determine conclusively that the lives of the Lutherans hang in the balance here.
If everyone in town hates the Lutherans, I suppose the first question would be: how did they get there in the first place? And the second would be: why do they stay?
In any case, there are opportunities created here. If the Lutherans felt that they absolutely must get food from this one specific grocer, some enterprising individual might turn a few dollars by buying the food then selling it to the Lutheran. In an all-Catholic town plus one Lutheran family, the guy who opens up a new, Lutheran-friendly grocery store has a built-in market that's one family larger than his competitor (the anti-Lutheran). Then it's up to the townsfolk to decide: do we prefer tolerance over intolerance? It's a consideration. Strictly from a business standpoint, intolerance is simply untenable. Do you disagree?
Incidentally (and I do mean incidentally), I am of the position that forcing institutional (therefore superficial) tolerance fosters a much more deeply embedded intolerance bred not only from whatever superstition fueled the intolerance, but also the antagonism reactive to the compulsion that government regulation represents. People in general really don't like being told what to do, and they certainly don't like being told how to think. Do you believe that's a legitimate position?