Is it sad that these people have to work on Thansgiving? Sure, I'll give you that.
However, if you feel bad for these people, please do so with the knowledge that these people don't have to be working for big retailers. There are hundreds of thousands of jobs available, and if working an occasional holiday makes you feel bad for these people, then get over it. They chose to work for the company who pays their paychecks.
I feel way more bad for military personnel that aren't even on the same side of the world as their family.