Just for you and other fussbudgets he should employ a staff to send appropriate cards to each of the various religions?
And you're positive that other religions wanted tolerance/fairness at the expense of Christ? Sure, they are always a few nutballs like my sister but I believe in the basic goodness of people in this world. Those people who just want to celebrate their Holy Days and not have them ignored, mocked or misunderstood.
I never have a problem with saying Merry Christmas because I don't allow political correctness to rule my feelings. And hey, if I offend someone, oh well. I certainly don't do it out of malice. If someone one wishes me a Happy Hanukkah or Kwanzaa I thank them with a smile and let them know I'm a Christian graciously.
There are many who don't believe Islam is the religion of peace but that doesn't stop him from saying it. It is Christmas. There is no other way to describe it even if you don't celebrate it. Christmas is no longer simply a religious holiday. Even atheists celebrate Christmas.