A company making money doesn't offend me in the least. That is, after all, what they're there for. If the customers are showing up (and clearly they are), go ahead and open.

Most employees are fully aware that irregular days and hours are a part of accepting a position in retail. Now, if Sears were informing employees the day before their shift that "oh by the way we are going to need you to come in tomorrow and if you don't you're fired," well, then I would have a problem. As it is, most of the folks helping you out on the holiday were aware well in advance, were compensated for their trouble, and were obviously not offended enough that they were willing to quit over the situation.