If there was no welfare, and no tax system, then introducing a minimum wage would probably be a net improvement.
However, taxes and welfare already address the issue of hungry people (I don't particularly care how angry a person is). My problem is not with the goal of redistributing wealth, but with the minimum wage as a way to do this. Since the tax authorities already know the figure that we are really interested in (how much money a person makes in total), it makes more sense to lower the tax rate on low income earners, or increase welfare, than to increase the minimum wage.