Laffy Kat being the voice of reason, weird.
If a Christian wishes me Merry Christmas, I reciprocate. If a Jew wishes me Happy Hannukkah, I'll say 'And to you, too!' If a Muslim gives me a salutation like good wishes for Eid al Futr, I wish blessings back to them. If a Pagan tells me happy Solstice, Yule, Saturnalia, or Turning of the Wheel, I give them back the same. It's not about me or trumpeting my own beliefs, it's about being civil, polite, and helping the other person to feel good and not break their mood or try to ruin their good cheer.