Through my 27+ years of pastoring, the question of the title of this post has arisen from several individuals on different occasions. I think it is a good question. It falls under "prove all things" (1 Thess 5:21). So let's begin first with the meetings of a church. I'll approach that with the regulative principle of worship.
Any element of worship not taught in scripture is forbidden. Our worship should be regulated by what God said. God has told us what He wants and we should give that to Him. Silence is not permission.
Does Christmas violate the regulative principle? I can't see it. Let me take you through my mental checklist. The incarnation of Christ, His virgin birth, is the truth. Singing is an element of worship in the Bible. Our church believes instrumental music is authorized by God's Word too. We see congregational, choir, and small group singing in scripture. If one preaches the Word of God, he will at some point preach about the incarnation, the Lord's first coming, His becoming a man. It's a teaching all over the Bible, so it is appropriate to preach those passages as an element of worship. That really does cover what we do in our church for Christmas. None of this is forbidden, because it's all in the Bible.
So what else matters in this, as it relates to the worship of a church meeting? Just really trying to be thorough here, but I think of practicing the above paragraph every year and using the term, "Christmas." Are those two actions violations of God's Word?
For the first one, I believe that the incarnation is worth singing and preaching about every year. The fact that we do this at the same time every December, since scripture doesn't tell us what time of the year Jesus' birth is, does not violate the regulative principle. I can preach about motherhood every mother's day and that doesn't conflict with the Bible. I have had Decembers where I just kept preaching whatever book I was covering, but not because it was wrong to stop and preach about Christ's birth. All the winter solstice stuff just seems like a red herring to me.
To me, using the term Christmas could be the most possible wrong practice, and I'm not convinced it is. Why? The big problem, it seems, is the "mas" part at the end of "Christmas." Is using the term "Christmas" supporting the Roman Catholic mass? Is using the term Easter supporting the worship of Ishtar? I don't believe it is.
I have read some about the history of the word "Christmas," like I'm sure some of you readers have. There is material all over the internet on this issue, so you can find it. It's hard to figure out what is true. English itself is a new language relative to the history of the world. It comes primarily from the Latin, a romantic language.
"Mass" comes from the Latin missa, which connects to the English words "dismissal" and "mission." At the institution of the Lord's Table, you might remember that Jesus and the disciples sang a hymn and went out. We do that at our church, that is, end with a hymn, then prayer, and go out. The original idea was that after prayer, singing, preaching, and other elements of worship, including the Lord's Table, another biblical element of worship, the saints were ready to be sent out on their mission, properly prepared for dismissal.
Churches assemble for edification and then disassemble for evangelism. The Father sent Jesus on His mission and the Lord Jesus sent us on the same mission. Are we dismissed or sent out every assembly to serve the Lord in the gospel?
Over a period of time, missa became "the eucharist," transubstantiation, and the whole Catholic liturgy. What was once a part of the order was now the whole thing. The word developed in its meaning, really perverted. The word for dismissal became the word for the entire order of Catholic worship.
"Christmas" is a word with an etymology. Maybe Catholics think "Christmas" is mass in its apostate form. Of course, Roman Catholics twist a lot of things, like a lot of other religions do too. You can't take every word and break it down into its etymology. People will say, "words mean things." They do, and in this case, Christmas doesn't mean "Catholic mass." "Christmas" means the celebration of Christ's birth.
I see using "Christmas" like using Wednesday, Thursday, or Saturday, except the latter has no connection to anything true at all, while missa actually does. I'm saying the latter are worse, so if someone shouldn't say "Christmas," then he shouldn't say "Wednesday" either. Wednesday is the "god" Woden, Thursday the god "Thor," and Saturday the "god" Saturn. But that's not what they mean to us. Are we really celebrating "Woden day" when we use "Wednesday"? Those three days just do not associate with false worship. They don't mean that to the people using them. I don't believe there is inherent meaning related to those false gods in the use of those terms. Get the following, because it's a scriptural argument. Shadrach, Meshach, and Abednego didn't stand against getting names that referred to pagan gods. That wasn't how they stood upon the Word of God. They kept those names, but they wouldn't violate dietary restrictions or bow before an idol, because those were taught in scripture.
I believe we have liberty to use the word "Christmas." That doesn't violate the regulative principle of worship.
What about the history of antagonism to Christmas? It's there. My interpretation of it is that it centers on Cromwellian England. Cromwell had some good points and a lot of bad ones too. The history of England revolves around religious conflicts, Protestantism versus Catholicism and the divine right of kings and its relationship to the English parliament.
OK, that seems like enough, but then we come to tinsel and trees and bulbs and presents. The regulative principle applies to corporate worship. That's how we argue that principle. Every life should be regulated by scripture. You should do what scripture says, but scripture is also silent on a lot. It does not tell you to listen to radios or not to listen to them. We've got to rely on principles to make these decisions. This is where Romans 14 and 1 Corinthians 6-10 come into play on this.
If the tree really is an act of worship like the Asherah pole or Gideon's ephod, then we should be rid of it. If you think it is, then don't have one. I don't think you should be picky on others who do have a tree. I believe you are violating Romans 14 when you are. Be picky on yourself.
I have never seen a Christmas tree used in a ceremony of worship. So how is it wrong? The tree itself isn't, any more than meat is wrong. It's a tree. I think the meat was worse in Corinth and Paul said it wasn't wrong to eat, unless it caused someone to stumble. There were ways that eating the meat was wrong, but it wasn't the meat. If I was convinced of a tree worship religion, I would get rid of my tree.
For a couple of years, my wife and I didn't set up a tree. Why? We were just starting as a church, had just a handful of people, two of which were a couple that had been taught that the tree was a sin. We did not want to hurt those two people's consciences. That was a 1 Corinthians 8-10 argument against the tree, but it was because of scruples these people had, which were not even legitimate. I don't know that I would do it again, but we did for a couple of Christmases. Now I'd probably just teach them what I'm writing here.
Here's another whole different issue -- Santa Claus. We don't have Santa in our home. Why? I think he's a replacement for Christ at Christmas. However, if you think that Christmas itself is pagan, then Santa Claus isn't any different than Christmas itself, or maybe better, because he's just a fictional character or the historical one, Nicholas, all depending on how you choose to see him. Because I think Santa is a replacement, we generally opt out on him. But that's not something I expect from or judge for everybody else. If a Christian got caught up in the Santa figure and talked like he was real, that would cross the line for me. I don't think parents should lie about who brought the presents.
I remember hearing a country western lyric as played by a roommate I had in college, and this is just out of my brain, because it stuck, "I don't believe in Santa Clause, but I believe what I believe in, and I believe in Santa's cause." Some people think that giving gifts is the cause of Christmas, and Santa represents Santa's cause. I'll let you judge that for yourself.