Oh what a perfectly fowl thing to say.
Because some people, like that Mom or, for that matter, the OP, are absolutely determined to see offense in anything they can, so that they can be pissed off and project their own hangups and insecurities onto others and make everyone as miserable as they are.
Some people just aren’t happy unless they’re not happy.
Gee, I wonder why? At least one person called you on it.
“Turkey Day” is just a cute colloquialism. Why act like a colossal jackass when somebody is trying to be nice?
Oh, and Thanksgiving is pretty much the only holiday I really look forward to every year. I can’t believe anyone would consider it “commercialized.”
But… they make you BUY the turkey! They should give it away, like Jesus and the Apostles did on Thanksgiving! 
When I was a youngster, my parents called the holiday “Turkey Day” because the term “Thanksgiving” implied thanking God, and my parents were hidebound atheists. For the same reason, Christmas was “Gift Day” and Easter was “Bunny Day.”
Thankful toward whom? I’m curious to know.
Toward the cook, of course.
Lighten up, dude.
The turkey almost became our national bird. If it had, we’d probably be eating bald eagles for Thanksgiving.
And if Miles Standish had shot a bobcat instead of a turkey, we’d all be eating pussy for Thanksgiving.
I hated Thanksgiving until I got married and could spend the holiday with someone who wasn’t going to give me shit about being a vegetarian at the dinner table every… single…year. It’s not commercialized so much as it is a tradition that’s supposed to be about giving thanks, but really is about gluttony now. I’m sure that’s not true for you (whoever is going to disagree with me and tell me that overeating is a way of giving thanks), but it is sorta true in a general sense, I think it’s safe to say.
Consequently, I think people are being too harsh on the OP. Everyone has turns of phrase that just irritate them, maybe irrationally, maybe with a rationale that you don’t buy, but nonetheless, I’m sure we all have our linguistic pet peeves. Mine are people who say “anywho” and “okeedokee” without irony. But I could see how “Turkey Day” might annoy someone, as it takes the focus off the giving of thanks and places it on the eating of massive amounts of food, which is goes back to my original point about it being Stuff Yer Face Day and not Thanksgiving anymore.
Sure, being annoyed by a particular phrase or usage is perfectly fine and dandy. Being outwardly and unnecessarily rude about it is not.
It sounded like the OP said this to a member of his family, so who knows what sort of familial irritation had been building up to that point? Some people find the holidays with family nerve-wracking, and it shows itself in little diatribes like the OP, keep that in mind.
I do think the OP has a valid point about changing the name of the holiday making it seem like it’s all about the food, which, let’s face it, is bloody well is, though we all pay lip service to the giving thanks part. Him saying so does not make him a jerk, as he was accused of being in his OP. What, he shouldn’t express his opinion because people luuuurve their turkey and can’t stand to have it pointed out that that’s not supposed to be the point of the holiday? I thought the turkey was the means (a family dinner) to an end (gratitude for a good harvest and family closeness). Anytime you say something that causes people to examine something they don’t want to examine, say, some sacred [del]bird[/del] cow holiday of theirs, they might not like it. Suck it up and don’t ruin the gorging for everyone, fusoya!
I’m biased because I have historically loathed Thanksgiving, and am not particularly fond of the moniker Turkey Day either, for reasons I’ve given. I sorta have to cheer the OP for having the nerve to point out that Thanksigiving, like that other fave, Christmas, has become more about conspicuous consumption than love and thanks and all that. Yeah, not a fan of the holiday season here, sorry. Is it Bunny Day yet? 
Let’s not forget the turkey rescuers.
Eh, the only reason Thanksgiving is a national holiday and not a footnote of history is because back in the mid-1800s, the editor of a monthly women’s magazine went on a huge letter-writing campaign (I’d read elsewhere that it went on for many years, though I don’t see a note about it in that article) and finally got then-President Lincoln to cave and issue a proclamation making it one. If it’s not as commercial a holiday in its popularization as Sweetest Day, it’s very close.
Thanksgiving has as much meaning as you want to give it.
(Oh, and thanks bbs2k, but I’m just worried about my mom and how she’s taking this news.)
And don’t forget Cecil’s take on that.
Duh! Thank you, I knew I’d read another article on it somewhere…
As others noted, the holiday was pretty much reinvented out of whole cloth for the sake of a tradition no one bothered to observe previously. And the reinventing revolved as much around turkey and cranberries and pumpkin pie as it did around grateful Calvinist Separatists and their Native American neighbors.
So, no, it doesn’t bother me to hear anyone call it “Turkey Day”. And I’m sure that they’re happy (read: thankful) to be spending a day with their family and enjoying the yummy meal that Mrs. Sarah Josepha Hale told us we should be eating.