Illustration of Grace (& Misunderstanding Grace); Matthew 20:1-16 - Parable of the Vineyard

Carrying this new deal being offered by this restaurant to its logical conclusion, they are actually charging those families and individuals who don't go to any church more money for their meal over those that those do go to church. Additionally, those tourists who may be visiting the area without a special bulletin will be charged more as well.

The above quote is taken from a post from the Mississippi Atheists website. What's clear, when one reads the post, is the author either doesn't understand the meaning of the word "discount" or he's prejudiced against grace shown to Christians, or both.

The situation is this: a restaurant advertised a 10% discount to customers who presented a copy of their church bulletin. The blogger suggested this was paramount to charging some people (who don't go to church) more than others.

This fails to understand how grace works. The owner, here, is not selling the food for two different prices, but for the same price, and yet has chosen to give a discount - (an amount the business owner could legitimately charge, as evidenced in the amount the business charges other customers - but an amount which the business owner chooses to absorb the loss and pass on benefit to the customers of his choosing.) Hence, it is not that other customers are being cheated (but are paying the price they justly owe), but that some - at the pleasure and expense of the business owner - are shown grace and thus experience more than they deserve.

I suspect the motivation behind the post is most clearly revealed in the writer's statement:

My initial question would be "Why is a church goer so much more favored at the restaurant over all others"?

Just as with the parable of the vineyard in Matthew 20:1-16, those who have a problem with those who dispense grace reveal a problem of the heart. Shouldn't we all enjoy seeing individuals experience grace and even see individuals who are willing to sacrifice so that others may experience more than they deserve? And doesn't the business owner have a right to choose how he will run his business and to whom he will show favor? Could the problem not be a social and ethical problem where one shows special treatment for specific subsets of people of a certain ideology over others, but rather a prejudice toward believers and a wrong attitude toward those who (justly and graciously) bless them?

(Note: I recognize this example is not without some weaknesses, but the essential point remains. Weaknesses include:
1. The grace of the gospel is different in that in this example the customers must perform an act - show a bulletin, whereas the grace of the gospel is such that it is completely without works on the part of the recipient.
2. In this illustration, there is incentive for the business owner which stands behind the marketing, whereas in the gospel the incentive to the one giving grace is not of the same nature as the benefit of the one receiving the grace.)