It potentially makes sense because Walmart employees are also part of the community, and Walmart doesn't pay very much. It also won't employ as many people as all the stores it displaces did.

Additionally, Walmart has extremely well-established multinational supply chains, and probably won't need to source much of its stock from the local community. If they do need to buy anything locally, they can pay absolutely rock-bottom prices once they've pushed out competitors and they are the only buyer.

If you shop at Walmart but otherwise have no other exposure to the retail sector, then as an individual you are probably financially better off. But looking at a community as a whole, the negative effects on retail employees and local suppliers apparently outweigh these individual gains.