Celebrate can suggest acknowledging an occasion by festivity. I suspect this is the definition Boomer objects to.
There is little to suggest a festive celebration in the poem "In Flanders Fields". Generally accepted as the impetus for Armistice Day, Remembrance Day and eventually Veterans Day.
Celebrate can also mean to perform a solemn ceremony, publicly and with appropriate rites.
It would seem that Boomer and Crash are both right.