I don't see how valid the argument for "sampling" the grapes is. There are very few other foods where you generally sample it before you buy it, people don't bat an eyelid when they buy meat, fish, dairy, other fruits etc without having a taste beforehand, why do they suddenly give a damn when it comes to grapes? This strikes me as a retroactive rationalisation of something that they know is wrong.
The foods that you do occasionally sample tend to be more pricey things like wine and cheese. This makes sense because you are paying good money for what you hope will be a good product. Grapes on the other hand are pretty damn cheap, so this argument is invalid. Furthermore, even sampling wine and cheese isn't a given. If you were to assume that you could sample it, then you would run into trouble before very long.
The foods that you do occasionally sample tend to be more pricey things like wine and cheese. This makes sense because you are paying good money for what you hope will be a good product. Grapes on the other hand are pretty damn cheap, so this argument is invalid. Furthermore, even sampling wine and cheese isn't a given. If you were to assume that you could sample it, then you would run into trouble before very long.