It doesn't surprise me that muslims celebrate christmas, given the fact that Jesus is an important prophet in Islam (known as Isa), celebrating his birth seems fairly straightforward. I'm agnostic but our Hindu neighbours in recent years have always brought us food and homemade sweets on Diwali. I've also been invited to share Iftar meals with a muslim colleague and his family during ramadan. It's nice to experience other cultures even if we don't share the same faith.
As for this outrage, I can't wrap my head around how fecking miserable and sad someones life must be if they get wound up by this. Life is finite as this year has proved. Why waste your energy on this nonsense. Probably the same types who celebrate St. Patricks day because their great great Grandparents once visited Cork. Arseholes.