I don't really have a problem if people want to think about Die Hard as a Christmas movie, but at best it's coincidental.
Same for When Harry Met Sally, I see folks out there saying it's a New Year's Eve/Day movie but that's a pretty loose association.
Is Planes, Trains and Automobiles a Thanksgiving movie? That might have a stronger case due to Steve Martin's character being motivated to return home in time for the holiday but not really a ton of Thanksgiving themes until the very end.
In the end, if a holiday coming up on the calendar inspires folks to watch certain movies, hey, go for it!