Interestingly enough, I've once been told it was bad that I said merry Christmas.

Context: I'm from a fairly irreligious country. Christmas has nothing to do with religion for me because our ancestors celebrated it long before the crusade and in our language it has nothing to do with Christ, we call it jõulud.

Anyway, my dad had a business in the US but his English was poor enough that when I was like 12 or 13, he asked me to send some emails to his clients for him. I did. This was in December. Next time he called, he said some client was furious because I either started or ended the email with Merry Christmas aaaand apparently it went to a Jewish family. Which I guess he knew beforehand but I did not and the didn't know the email was from me, not him.

This would've been like late 00s.