Joseph Morrison Skelly pens a fine article focusing especially on Dietrich Bonhoeffer's experience of Christmas in prison at the hands of the German Gestapo:
For two millennia, tyrants have suppressed word of the birth of Christ
or religious 
commemorations of it. Herod feared for his throne. In the
modern era, dictators have
realized that the potential for human
freedom inherent in this divine event threatens to undermine their
authoritarian rule. Liberty, not servitude, is the logical outcome of a
process whereby men and women channel their allegiance not simply to a
secular leader but ultimately to a heavenly being, and, at the same
time, governments accept the principle that temporal power must take
account of a higher moral law. In the recent past, and today, despots
in the Soviet Union, Eastern Europe, Nazi Germany, China, Cuba, North
Korea, and elsewhere have sought to suppress man’s relationship with
God. . .
But the light will not be extinguished. Christians in unfree lands —
including places where religious extremists restrict their rights, such
as Saudi Arabia — have enacted the second part of this historical
pattern: they have resisted oppression by celebrating Christmas, often
in secret, sometimes in open defiance, frequently without fear. This
year will be no different, as they commemorate Christ’s birth and so
defend religious freedom . . .
More . . .