In his blog post What Do the Likes of Paul Krugman, Robert Reich, and Barack Obama Know That the Swiss Miss? (Answer: Nothing) Don Boudreaux sums it up perfectly. Here's his closing paragraph:
Low-skilled workers have a difficult enough time of it as it is. Their best hope for finding and keeping gainful employment is their willingness to work for less pay than more-skilled workers demand. Minimum-wage legislation strips from low-skilled workers this option, one of their premier bargaining chips. Ponder this reality if you’re ever tempted to think of minimum-wage supporters as being enlightened and humane. They might be one or the other, but they are certainly not both.