Each to it's own.
Salah has the right to do whatever he wishes to do inside his home and as long as it does not break law of the land. I have no problem with him.
For me personally though, and sorry, non-Muslims may not understand this, but EVEN if it's celebrated as a "Holiday", then what Holiday is this for? Obviously to celebrate Christmas. A Christian who may be celebrating these "Holidays" may not attend the Church but many who celebrate, DO attend the Church.
Yes, the religious aspect of Christmas Holidays be on the slight decline in the west but lets not kid ourselves. There are 100 and MILLIONS of people ALL OVER THE WORLD who celebrate Christmas by attending the church with their families and kids.
Why wishful thinking by taking shelter under the term "in the west"? How about Christmas Holidays in Philippines and Christian countries in the East, South America and in Africa?
ohhhh, you just want to
"copy the west, don't you??"

Well, good for you.
For me personally, I gladly greet Christians and support their celebration of the event, but personally I won't celebrate Christmas because it opens up the possibility of agreeing to Shirk. This goes against the very basic foundation of Islamic Aqeeda.
If you celebrate Christmas in any form, what you agree to is that "Jesus is God and the Son of God".
I have no problem whoever believes in this, but for me personally, it's shirk. I can't agree to it for my personal belief and for my personal faith.
Salah or whoever thinks differently has the choice to do so, and I have no problem with it.
I think, in a large aspect of our lives, God has given the ability to choose. And we should make wise choices because in the end, we will be responsible for our choices.
And for those, talking about Muslim getting married to Christians. I am not a religious scholar but my personal belief is that it's valid only if you are marrying a Christian who believes in the original Christianity which was widely practiced in the first 300 years of Christianity where the followers of Jesus believed Jesus to be a prophet of God and they refrained from eating pork, just as Jesus did.
If you find such a Christian girl then yes, but many modern day Christians commit shirk when they state that Jesus is God or Jesus is the Son of God. This is their belief and I don't have an issue with it but I don't think a Muslim is allowed to marry a Mushrik.