Yeah. That sort of policy encourages ALDI to sell their bread at the equally high price rather than the low price. It's a bit like the minimum wage. If you enforce a price floor, they will just sell less (just like employers hire less). Those who are poor and cannot afford the high price will not experience a competitive price, because ALDI will have to bundle the decision of lowering the price locally with lowering the price nationally - which will cause more costs than benefits for them.
Basically speaking, it doesn't produce efficiency because instead of being able to freely change the local prices to match local demand and supply, they have to make a trade-off between meeting demand and supply in location A and location B. The social responsibility sounds all nice and fairy-tale like, but the truth is that you will see ALDI being less competitive than they previously were in the competitive areas (with lots of supermarkets). Simply put, they will conclude that the costs of being competitive in one location far outweigh the loss in revenue all across the board.