My local Hasidic Rabbi took the night off last night. He didn't speak between mincha and maariv, and he didn't appear at his regular Sunday night shiur. Why? Because it was Nitl Nacht, and on Nitl Nacht it is his custom to act like a mourner and forgo all Torah learning.
A few notes on the practice:
1 - It's hard to fathom. My local Hasidic Rabbi ignores July fourth. Memorial Day is not remembered. He goes to work on Thanksgiving. None of those days exist on his calendar. If he is going to ignore days that celebrate events from which he has benefited, how can he justify his recognition of Orthodox Christmas? Even a negative recognition is recognition. Memorial Day is not within a Hasid's ken; but Christmas is. That's topsy-tursvy.
2 - According to Miriam Shaviv, Hasidim abstain from Torah study because they "don't want to bring about such improvements [to the world through their Torah study] at a time when the Christian majority is devoutly steeped in their prayers, lest outsiders believe the improvement came from the Christian worship." Fabulous, only if that that's your concern, why not fast from Torah study on Easter Sunday, or, for that matter, on Super Bowl Sunday when the betting halls probably contain as much prayer as any church.
A second justification for the custom is that often we dedicate Torah study to the memory of revered Rabbis and beloved ancestors. If we studied on Christmas, the argument goes, someone might mistake Jesus for a revered Rabbi. Worse, he might accrue credit on his heavenly account in the merit of our learning.
To the first concern I reply: Bwahaha. Not even the very worst sort of Cross-loving GOP-Jew is likely to mistake Jesus for a revered Rabbi. (I hope) To the second concern, I say "so what?" The real Jesus was a Jew who cared about other Jews. He had no intention of abolishing Judaism, or of establishing a church that would seek to destroy his people. If the clerk in charge of divine credit is stupid enough to think that my Christmas Eve learning is meant to be deposited on Jesus' account, I have no objection. (though I will suggest that the Almighty hire a clerk who doesn't have his head up his rear end)
3 - The common justification for the Heredi refusal to pause for the siren on Israeli Memorial day is that it is bitul Torah. Can you explain to me why two minutes to honor Israeli war dead is impossible, while a full night (Sorry! Two full nights: Many Hasidim abstain on Orthodox Christmas, too) without learning has become accepted?