As an explanation of why we celebrate Christmas each year, the above video is superb and concise.
The words of Linus are of course taken from the Gospel of Saint Luke:
And there were in the same country shepherds abiding in the field, keeping watch over their flock by night.
And, lo, the angel of the Lord came upon them, and the glory of the Lord shone round about them: and they were sore afraid.
And the angel said unto them,
Fear not: for, behold, I bring you good tidings of great joy, which shall be to all people.
For unto you is born this day in the city of David a Saviour, which is Christ the Lord.
And this shall be a sign unto you; Ye shall find the babe wrapped in swaddling clothes, lying in a manger.
And suddenly there was with the angel a multitude of the heavenly host praising God, and saying,
Glory to God in the highest, and on earth peace, good will toward men.
When I was a boy the Charlie Brown Christmas Special was my favorite TV Christmas Special. As a man, I agree. Hard to believe it is now over a half century since I first viewed it.
Donald R. McClarey
Paul Zummo
Almost Chosen People 
“Glory to God in the highest, and on earth peace, goodwill toward men.” Is very wrongly interpreted and thereby departs from the righteous Christ message that it truly is.
A fair modern translation would read: “ Glory to God in the highest; and on earth peace to men of good will.”.
Another interpretation reads: “ Glory to God in the highest; and on earth peace among men with whom He is pleased..
Look at original Greek or even 4th century Latin Vulgate and you will see that the blessing is for whom God is pleased, not for the ones who reject Christ or His message.
Thr Linus version was interpreted in malice of the true message of Christ. It reduces Christianity to a “do what you feel is good” message from of “pick up your cross and become like Christ” message.