I think it's an argument somewhat like the "don't water your lawn in a drought" argument - even in aggregate, domestic/consumer impact is miniscule. 2005 numbers say that domestic water use is 8.5% of freshwater use, and of that, irrigation is at most 5.3% (the "other" category). Yet we in California were told to let our lawns die or given money to convert to high-efficiency landscape.

An average shower uses 17 gallons of water. A single pound of almonds uses 1,900 gallons.

Anyway, all this to say that I think the GP's argument is convincing.