If a person can't get a Thanksgiving turkey, can they eat fast food such as pizza, burgers, fries, etc?

Yes they can, I had Applebee’s for Thanksgiving dinner since I was alone with my son.  

Why not? I've had enchiladas a few times on Thanksgiving. I hate turkey. Make sure the FF you want is open though, a lot close on Thanksgiving, as it's a national holiday. You might be able to get it the day before or early in the day, but past noon, prolly not gonna happen.

You can have / eat want you choose and when to eat it.

Yes if thats what they choose to do 

Sure.  I've had pizza for Thanksgiving several times, and I know others who have as well. The idea is to give thanks, not to eat Turkey!

What would stop them, genius?

They could have ham.  One year - we had duck instead of turkey.  We have also done Cornish hens instead of turkey.  

People could eat fast food instead - if they can find someplace that is open.

Really - they could eat anything they wanted to.  It doesn't have to be a "traditional" dinner.  

You can eat whatever you would like.

Sure, if your neighborhood fast food place is open! Sounds better than turkey!

They can, but they shouldn't.  Well, maybe the pizza would be ok.