I love this one, of course it's a Christmas movie:
The entire reason they're at the setting is "Christmas party"
"Ho Ho Ho now I have a machine gun"
"Not a creature was stirring, except four assholes coming in the rear" (also, phrasing lol)
"It's Christmas Theo, it's the time of miracles, so be of good cheer"
both scenes I can remember with Argyle mention Christmas by name.
It's undebatably a Christmas movie, but why I love it is because when people object it gives me the opportunity to make it worse by informing them that Rambo: First Blood is too.
But neither of those are my favorite Christmas movie, that honor goes to Gremlins.
I think Lethal Weapon has more of a Christmas message than Die Hard - Mismatched couple work through their differences to overcome adversity and finally spend Christmas Day together. That's a Hallmark pitch if ever there was one.
If it's about a romance during wartime, it is both a romance and a war movie, just as Kelly's Heroes is a heist film, a war movie, and a comedy a rolled into one. If it's about German terrorists taking over a Christmas party and being thwarted with a lot of action by a cop, it's a Christmas movie, a cop movie, and an action movie.
And Top Gun is a romance movie, a gay romance movie. Who can forget "playing with the boys?" (Not passing judgement, if Mavrick got Goose's goose that's between them and Iceman!)