If this is about Detroit and not Flint then not having access to clean water is strictly an economic issue and not a structural one. In other words, the people are too poor to pay the water bill and the city has shut it off as a result. I'm going to go out on a limb here and say people in this situation don't have the economic luxury of deciding to be vegan. Most of them are probably pennies away from choosing between going hungry, trapping rats and pigeons for food, or robbing convenience stores. The ones who aren't quite that desperate aren't much better off and being that choosy about diet isn't a realistic option. Just sourcing enough variety of vegan foods to make a healthy diet is probably next to impossible where these people live, and if you don't have water, odds are you don't have much access to transportation either.
PETA, as usual, are just being opportunistic dicks and exploiting an unrelated tragedy to further their agenda with the full knowledge that they won't actually have to lift a finger or write a cheque to help anyone because the hurdle to receive their help is too high.