“Night of the Long Knives” was an attack of Nazi’s against other Nazis; a purge of the ranks. If the attack on creches was like “Night of the Long Knives” it would be Christians attacking and destroying Christmas creches. (A good comparison only if fundamentalists are making these attacks, and I don’t think that’s the case.)
I think what you really mean is that this attack on creches is like the ***kristallnacht, ***or the “crystal night,” when Jewish homes and storefronts were attacked and ransacked by the Nazis.
Night of the Long Knives:
en.wikipedia.org/wiki/Night_of_the_long_knives
Crystal Night:
en.wikipedia.org/wiki/Kristallnacht