I'm not really a Thanksgiving purist. There have been just as many Thanksgivings where I've had pizza, Chinese food, and sushi, as there have been ones where I've had turkey. The whole holiday is actually sort of a non-event, as far as I'm concerned. Just an excuse to take off a couple of days off from work, enjoy the novelty of watching football on a weekday, and then braving the stores the next day so you can buy crap you didn't realize you wanted until you saw the Black Friday circulars.
However, Thanksgiving at McDonald's just seems wrong. Borderline un-American, in fact. I realize that the people who would even consider going to McDonald's on Thanksgiving aren't doing so because they really want to, but because they likely fall into two categories: people without friends or family they can join, or people who can't really afford anything else.
There are better options out there. Take that money you would spend on a Big Mac meal, and buy cold cuts and instant stuffing. That's better than McDonald's on Thanksgiving. Rent a movie and get a box of microwave kettle corn. That's better than McDonald's on Thanksgiving. Put on some old clothes, head over to a homeless shelter, and have Thanksgiving dinner there. That's better than McDonald's on Thanksgiving. Pretty much anything you can think of is better than McDonald's on Thanksgiving.
Of course, it'd be different if they brought the McRib back. Then it would be awesome.