This is true at a fundamental level in that we need food to eat but there is a really strong argument that a huge fraction of the agricultural water use in the American west is not "useful" or at least should pay market rate. Examples include flood irrigation which could be readily converted to drip and reduce water usage or growing animal feed (particularly for export), simply stop doing these here and do it in places with more water.
This is basically a straw man, no one is saying to stop growing food to save water, but we can save a lot of water without anyone starving. Beef would be more expensive and some other countries would lose cheap imported feed (alfalfa, teff, etc).
