It is not a question of whether it is right or wrong for a non-religious person, particularly atheist or agnostic, to celebrate Christian holidays. It is a question of whether it is appropriate. There are many Christians and atheists who firmly stand for their beliefs, and for many circumstantial disputes, the only way to make peace with each other is to agree to disagree; to respect each other’s religious beliefs (or lack thereof).
Christmas is probably the most widely celebrated holiday, by Christians and non-religious personnel alike. Out of respect, those who do not recognize the Reason of the Season (the Coming and Birth of Christ) should not partake in the celebration. Would it not be disrespectful for a Christian to light a menorah and walk around ‘celebrating’ Hanukah, just for the sole hope to receive presents and have a reason to party? April 1st is National Atheist Day; would it not be disrespectful for bands of Christians to gather together and throw a party on the behalf of atheism, even though they clearly do not agree with the underlying beliefs? More than likely the response would be ‘no, it isn’t appropriate, it disrespects both groups.’
Many atheists argue that celebrating Christmas is acceptable even if the reason is not religiously based because the origin of December 25 as a holiday dates back before the coming of Christ. That in fact, the day was celebrated as a pagan holiday, and therefore was a celebration that does not ‘belong’ to Christians. This argument has reasonable structure if atheists celebrated on the behalf of pagan gods. However, since atheists do not believe in the existence of any creator, pagan or Christian, this argument offers no foundation.
Another argument that often presents itself is that it is human nature to gather with family and friends and celebrate, so it is perfectly reasonable for atheists to celebrate holiday seasons with their family members who may be Christians. While I do think it is true, it is important to take a break from the daily routine to celebrate with loved ones, it is not required to use certain holidays like Christmas or Easter, or even holidays most people forget are religiously based like Valentine’s Day or Mardi Gras. There are many holidays that are not faith oriented, such as Independence Day or New Year’s Day, that would be more than appropriate to join together with friends and family. Celebrating with loved ones can take place any day of the year; it should not be required or restricted to Christmas or Easter. Gifts and hugs can be exchanged anytime, but if that is going to be the only reason to celebrate a holiday that respects God, then it is best not to celebrate it at all.